diff --git a/.gitignore b/.gitignore
new file mode 100644
index 00000000..807840a3
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,43 @@
+__pypackages__/
+__pycache__/
+*.py[cod]
+*$py.class
+*.so
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+htmlcov/
+cover/
+target/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+*.manifest
+*.spec
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+*.py,cover
+.hypothesis/
+.pytest_cache/
+.pybuilder/
+.env
+.venv
+
diff --git a/inotify-instances b/inotify-instances
deleted file mode 100755
index 86c1132b..00000000
--- a/inotify-instances
+++ /dev/null
@@ -1,113 +0,0 @@
-#!/usr/bin/env python3
-
-"""
-Expose Linux inotify(7) instance resource consumption.
-
-Operational properties:
-
-  - This script may be invoked as an unprivileged user; in this case, metrics
-    will only be exposed for processes owned by that unprivileged user.
-
-  - No metrics will be exposed for processes that do not hold any inotify fds.
-
-Requires Python 3.5 or later.
-"""
-
-import collections
-import os
-import sys
-from prometheus_client import CollectorRegistry, Gauge, generate_latest
-
-
-class Error(Exception):
-    pass
-
-
-class _PIDGoneError(Error):
-    pass
-
-
-_Process = collections.namedtuple(
-    "Process", ["pid", "uid", "command", "inotify_instances"])
-
-
-def _read_bytes(name):
-    with open(name, mode='rb') as f:
-        return f.read()
-
-
-def _pids():
-    for n in os.listdir("/proc"):
-        if not n.isdigit():
-            continue
-        yield int(n)
-
-
-def _pid_uid(pid):
-    try:
-        s = os.stat("/proc/{}".format(pid))
-    except FileNotFoundError:
-        raise _PIDGoneError()
-    return s.st_uid
-
-
-def _pid_command(pid):
-    # Avoid GNU ps(1) for it truncates comm.
-    # https://bugs.launchpad.net/ubuntu/+source/procps/+bug/295876/comments/3
-    try:
-        cmdline = _read_bytes("/proc/{}/cmdline".format(pid))
-    except FileNotFoundError:
-        raise _PIDGoneError()
-
-    if not len(cmdline):
-        return "<zombie>"
-
-    try:
-        prog = cmdline[0:cmdline.index(0x00)]
-    except ValueError:
-        prog = cmdline
-    return os.path.basename(prog).decode(encoding="ascii",
-                                         errors="surrogateescape")
-
-
-def _pid_inotify_instances(pid):
-    instances = 0
-    try:
-        for fd in os.listdir("/proc/{}/fd".format(pid)):
-            try:
-                target = os.readlink("/proc/{}/fd/{}".format(pid, fd))
-            except FileNotFoundError:
-                continue
-            if target == "anon_inode:inotify":
-                instances += 1
-    except FileNotFoundError:
-        raise _PIDGoneError()
-    return instances
-
-
-def _get_processes():
-    for p in _pids():
-        try:
-            yield _Process(p, _pid_uid(p), _pid_command(p),
-                           _pid_inotify_instances(p))
-        except (PermissionError, _PIDGoneError):
-            continue
-
-
-def _get_processes_nontrivial():
-    return (p for p in _get_processes() if p.inotify_instances > 0)
-
-
-def main(args_unused=None):
-    registry = CollectorRegistry()
-
-    g = Gauge('inotify_instances', 'Total number of inotify instances held open by a process.',
-              ['pid', 'uid', 'command'], registry=registry)
-
-    for proc in _get_processes_nontrivial():
-        g.labels(proc.pid, proc.uid, proc.command).set(proc.inotify_instances)
-    print(generate_latest(registry).decode(), end='')
-
-
-if __name__ == "__main__":
-    sys.exit(main(sys.argv))
diff --git a/inotify_instances.py b/inotify_instances.py
new file mode 100755
index 00000000..5eb8e599
--- /dev/null
+++ b/inotify_instances.py
@@ -0,0 +1,209 @@
+#!/usr/bin/env python3
+
+"""
+Expose Linux inotify(7) instance resource consumption.
+
+Operational properties:
+
+  - This script may be invoked as an unprivileged user; in this case, metrics
+    will only be exposed for processes owned by that unprivileged user.
+
+  - No metrics will be exposed for processes that do not hold any inotify fds.
+
+Requires Python 3.5 or later.
+"""
+
+import argparse
+import collections
+import os
+import re
+import sys
+
+from prometheus_client import CollectorRegistry, Gauge, generate_latest
+
+__doc__ = "Exponse Linux Kernel inode information as Prometheus metrics."
+_NotifyTarget = "anon_inode:inotify"
+_Proc = "/proc"
+_CommFile = "cmdline"
+_StatsFile = "status"
+_DescriptorDir = "fd"
+
+
+class Error(Exception):
+    pass
+
+
+class _PIDGoneError(Error):
+    pass
+
+
+_Process = collections.namedtuple(
+    "Process", ["pid", "uid", "command", "inotify_instances"]
+)
+
+
+def _read_bytes(name):
+    with open(name, mode="rb") as f:
+        return f.read()
+
+
+def _pids(proc=_Proc):
+    for n in os.listdir(proc):
+        if not n.isdigit():
+            continue
+        yield int(n)
+
+
+def _pid_uid(status):
+    try:
+        s = os.stat(status)
+    except FileNotFoundError:
+        raise _PIDGoneError()
+    return s.st_uid
+
+
+def _pid_command(cmdline):
+    # Avoid GNU ps(1) for it truncates comm.
+    # https://bugs.launchpad.net/ubuntu/+source/procps/+bug/295876/comments/3
+    try:
+        cmdline = _read_bytes(cmdline)
+    except FileNotFoundError:
+        raise _PIDGoneError()
+
+    if not len(cmdline):
+        return "<zombie>"
+
+    try:
+        prog = cmdline[0:cmdline.index(0x00)]
+    except ValueError:
+        prog = cmdline
+    return os.path.basename(prog).decode(encoding="ascii", errors="surrogateescape")
+
+
+def _pid_inotify_instances(descriptors):
+    instances = 0
+    try:
+        for fd in os.listdir(descriptors):
+            try:
+                target = os.readlink(os.path.join(descriptors, fd))
+            except FileNotFoundError:
+                continue
+            if target == _NotifyTarget:
+                instances += 1
+    except FileNotFoundError:
+        raise _PIDGoneError()
+    return instances
+
+
+def _get_processes(proc=_Proc):
+    for p in _pids(proc):
+        try:
+            pid = str(p)
+            status = os.path.join(proc, pid, _StatsFile)
+            cmdline = os.path.join(proc, pid, _CommFile)
+            descriptors = os.path.join(proc, pid, _DescriptorDir)
+            yield _Process(
+                p,
+                _pid_uid(status),
+                _pid_command(cmdline),
+                _pid_inotify_instances(descriptors),
+            )
+        except (PermissionError, _PIDGoneError):
+            continue
+
+
+def _generate_process_metrics(command=None, users=[], proc=_Proc):
+    registry = CollectorRegistry()
+    namespace = "inotify"
+
+    g = Gauge(
+        "instances",
+        "Total number of inotify instances held open by a process.",
+        ["pid", "uid", "command"],
+        namespace=namespace,
+        registry=registry,
+    )
+
+    for proc in _get_processes(proc):
+        if proc.inotify_instances <= 0:
+            continue
+        elif users and proc.uid not in users:
+            continue
+        elif command and not command.match(proc.command):
+            continue
+
+        g.labels(proc.pid, proc.uid, proc.command).set(proc.inotify_instances)
+
+    return generate_latest(registry).decode()
+
+
+def _generate_user_metrics(users=[], proc=_Proc):
+    registry = CollectorRegistry()
+    namespace = "inotify"
+
+    g = Gauge(
+        "user_instances",
+        "Total number of inotify instances held open by a user.",
+        ["uid"],
+        namespace=namespace,
+        registry=registry,
+    )
+
+    for proc in _get_processes(proc):
+        if proc.inotify_instances <= 0:
+            continue
+        elif users and proc.uid not in users:
+            continue
+
+        g.labels(proc.uid).inc()
+
+    return generate_latest(registry).decode()
+
+
+def main(argv=[__name__]):
+    parser = argparse.ArgumentParser(
+        prog=os.path.basename(argv[0]),
+        exit_on_error=False,
+        description=__doc__,
+    )
+    parser.add_argument(
+        "-c",
+        "--command",
+        default=".+",
+        type=re.compile,
+        dest="command",
+        metavar="REGEX",
+        help="Filter metrics based on the process command",
+    )
+    parser.add_argument(
+        "-u",
+        "--user",
+        action="append",
+        type=int,
+        dest="users",
+        metavar="UID",
+        help="Filter metrics based on the process user",
+    )
+    parser.add_argument(
+        "-U",
+        "--user-summary",
+        action="store_true",
+        dest="user_summary",
+        help="Generate per-user metric summaries instead of per process",
+    )
+
+    try:
+        args = parser.parse_args(argv[1:])
+    except argparse.ArgumentError as err:
+        print(err, file=sys.stderr)
+        return 1
+
+    if args.user_summary:
+        print(_generate_user_metrics(args.users), end="")
+    else:
+        print(_generate_process_metrics(args.command, args.users), end="")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main(sys.argv))
diff --git a/mock/fixtures/inotify_instances/1/cmdline b/mock/fixtures/inotify_instances/1/cmdline
new file mode 100755
index 00000000..7ef00dc3
Binary files /dev/null and b/mock/fixtures/inotify_instances/1/cmdline differ
diff --git a/mock/fixtures/inotify_instances/1/fd/0 b/mock/fixtures/inotify_instances/1/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1/fd/1 b/mock/fixtures/inotify_instances/1/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1/fd/12 b/mock/fixtures/inotify_instances/1/fd/12
new file mode 120000
index 00000000..0a39b5fd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1/fd/12
@@ -0,0 +1 @@
+anon_inode:inotify
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1/fd/123 b/mock/fixtures/inotify_instances/1/fd/123
new file mode 120000
index 00000000..0a39b5fd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1/fd/123
@@ -0,0 +1 @@
+anon_inode:inotify
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1/fd/324 b/mock/fixtures/inotify_instances/1/fd/324
new file mode 120000
index 00000000..0a39b5fd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1/fd/324
@@ -0,0 +1 @@
+anon_inode:inotify
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1/fd/5 b/mock/fixtures/inotify_instances/1/fd/5
new file mode 120000
index 00000000..0a39b5fd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1/fd/5
@@ -0,0 +1 @@
+anon_inode:inotify
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1/fd/82 b/mock/fixtures/inotify_instances/1/fd/82
new file mode 120000
index 00000000..0a39b5fd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1/fd/82
@@ -0,0 +1 @@
+anon_inode:inotify
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1/fd/90 b/mock/fixtures/inotify_instances/1/fd/90
new file mode 120000
index 00000000..0a39b5fd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1/fd/90
@@ -0,0 +1 @@
+anon_inode:inotify
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1/status b/mock/fixtures/inotify_instances/1/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/1016/cmdline b/mock/fixtures/inotify_instances/1016/cmdline
new file mode 100755
index 00000000..8d131f4d
Binary files /dev/null and b/mock/fixtures/inotify_instances/1016/cmdline differ
diff --git a/mock/fixtures/inotify_instances/1016/fd/0 b/mock/fixtures/inotify_instances/1016/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1016/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1016/fd/1 b/mock/fixtures/inotify_instances/1016/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1016/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1016/status b/mock/fixtures/inotify_instances/1016/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1016/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/1017/cmdline b/mock/fixtures/inotify_instances/1017/cmdline
new file mode 100755
index 00000000..a4b45c0d
Binary files /dev/null and b/mock/fixtures/inotify_instances/1017/cmdline differ
diff --git a/mock/fixtures/inotify_instances/1017/fd/0 b/mock/fixtures/inotify_instances/1017/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1017/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1017/fd/1 b/mock/fixtures/inotify_instances/1017/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1017/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1017/status b/mock/fixtures/inotify_instances/1017/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1017/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/1024/cmdline b/mock/fixtures/inotify_instances/1024/cmdline
new file mode 100644
index 00000000..a93cff7b
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1024/cmdline
@@ -0,0 +1 @@
+/usr/local/bin/rsyslogd
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1024/fd/0 b/mock/fixtures/inotify_instances/1024/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1024/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1024/fd/1 b/mock/fixtures/inotify_instances/1024/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1024/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1024/status b/mock/fixtures/inotify_instances/1024/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1024/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/1025/cmdline b/mock/fixtures/inotify_instances/1025/cmdline
new file mode 100755
index 00000000..03d855be
Binary files /dev/null and b/mock/fixtures/inotify_instances/1025/cmdline differ
diff --git a/mock/fixtures/inotify_instances/1025/fd/0 b/mock/fixtures/inotify_instances/1025/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1025/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1025/fd/1 b/mock/fixtures/inotify_instances/1025/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1025/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1025/status b/mock/fixtures/inotify_instances/1025/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1025/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/1051/cmdline b/mock/fixtures/inotify_instances/1051/cmdline
new file mode 100755
index 00000000..d811d4ec
Binary files /dev/null and b/mock/fixtures/inotify_instances/1051/cmdline differ
diff --git a/mock/fixtures/inotify_instances/1051/fd/0 b/mock/fixtures/inotify_instances/1051/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1051/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1051/fd/1 b/mock/fixtures/inotify_instances/1051/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1051/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1051/status b/mock/fixtures/inotify_instances/1051/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1051/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/1189/cmdline b/mock/fixtures/inotify_instances/1189/cmdline
new file mode 100755
index 00000000..b3918bbc
Binary files /dev/null and b/mock/fixtures/inotify_instances/1189/cmdline differ
diff --git a/mock/fixtures/inotify_instances/1189/fd/0 b/mock/fixtures/inotify_instances/1189/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1189/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1189/fd/1 b/mock/fixtures/inotify_instances/1189/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1189/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/1189/status b/mock/fixtures/inotify_instances/1189/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/1189/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/2787/cmdline b/mock/fixtures/inotify_instances/2787/cmdline
new file mode 100755
index 00000000..a0aca6d1
Binary files /dev/null and b/mock/fixtures/inotify_instances/2787/cmdline differ
diff --git a/mock/fixtures/inotify_instances/2787/fd/0 b/mock/fixtures/inotify_instances/2787/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/2787/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/2787/fd/1 b/mock/fixtures/inotify_instances/2787/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/2787/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/2787/status b/mock/fixtures/inotify_instances/2787/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/2787/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/3376/cmdline b/mock/fixtures/inotify_instances/3376/cmdline
new file mode 100755
index 00000000..6be6295f
Binary files /dev/null and b/mock/fixtures/inotify_instances/3376/cmdline differ
diff --git a/mock/fixtures/inotify_instances/3376/fd/0 b/mock/fixtures/inotify_instances/3376/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/3376/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/3376/fd/1 b/mock/fixtures/inotify_instances/3376/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/3376/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/3376/status b/mock/fixtures/inotify_instances/3376/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/3376/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/512/cmdline b/mock/fixtures/inotify_instances/512/cmdline
new file mode 100755
index 00000000..4a4cae8c
Binary files /dev/null and b/mock/fixtures/inotify_instances/512/cmdline differ
diff --git a/mock/fixtures/inotify_instances/512/fd/0 b/mock/fixtures/inotify_instances/512/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/512/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/512/fd/1 b/mock/fixtures/inotify_instances/512/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/512/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/512/fd/23 b/mock/fixtures/inotify_instances/512/fd/23
new file mode 120000
index 00000000..0a39b5fd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/512/fd/23
@@ -0,0 +1 @@
+anon_inode:inotify
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/512/fd/30 b/mock/fixtures/inotify_instances/512/fd/30
new file mode 120000
index 00000000..0a39b5fd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/512/fd/30
@@ -0,0 +1 @@
+anon_inode:inotify
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/512/fd/34 b/mock/fixtures/inotify_instances/512/fd/34
new file mode 120000
index 00000000..0a39b5fd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/512/fd/34
@@ -0,0 +1 @@
+anon_inode:inotify
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/512/fd/35 b/mock/fixtures/inotify_instances/512/fd/35
new file mode 120000
index 00000000..0a39b5fd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/512/fd/35
@@ -0,0 +1 @@
+anon_inode:inotify
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/512/fd/41 b/mock/fixtures/inotify_instances/512/fd/41
new file mode 120000
index 00000000..0a39b5fd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/512/fd/41
@@ -0,0 +1 @@
+anon_inode:inotify
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/512/fd/890 b/mock/fixtures/inotify_instances/512/fd/890
new file mode 120000
index 00000000..0a39b5fd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/512/fd/890
@@ -0,0 +1 @@
+anon_inode:inotify
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/512/status b/mock/fixtures/inotify_instances/512/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/512/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/547/cmdline b/mock/fixtures/inotify_instances/547/cmdline
new file mode 100755
index 00000000..20ef68d3
Binary files /dev/null and b/mock/fixtures/inotify_instances/547/cmdline differ
diff --git a/mock/fixtures/inotify_instances/547/fd/0 b/mock/fixtures/inotify_instances/547/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/547/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/547/fd/1 b/mock/fixtures/inotify_instances/547/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/547/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/547/status b/mock/fixtures/inotify_instances/547/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/547/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/548/cmdline b/mock/fixtures/inotify_instances/548/cmdline
new file mode 100755
index 00000000..7178672d
Binary files /dev/null and b/mock/fixtures/inotify_instances/548/cmdline differ
diff --git a/mock/fixtures/inotify_instances/548/fd/0 b/mock/fixtures/inotify_instances/548/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/548/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/548/fd/1 b/mock/fixtures/inotify_instances/548/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/548/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/548/status b/mock/fixtures/inotify_instances/548/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/548/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/557/cmdline b/mock/fixtures/inotify_instances/557/cmdline
new file mode 100755
index 00000000..2730100a
Binary files /dev/null and b/mock/fixtures/inotify_instances/557/cmdline differ
diff --git a/mock/fixtures/inotify_instances/557/fd/0 b/mock/fixtures/inotify_instances/557/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/557/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/557/fd/1 b/mock/fixtures/inotify_instances/557/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/557/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/557/status b/mock/fixtures/inotify_instances/557/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/557/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/569/cmdline b/mock/fixtures/inotify_instances/569/cmdline
new file mode 100755
index 00000000..ffb9d461
Binary files /dev/null and b/mock/fixtures/inotify_instances/569/cmdline differ
diff --git a/mock/fixtures/inotify_instances/569/fd/0 b/mock/fixtures/inotify_instances/569/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/569/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/569/fd/1 b/mock/fixtures/inotify_instances/569/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/569/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/569/status b/mock/fixtures/inotify_instances/569/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/569/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/7038/cmdline b/mock/fixtures/inotify_instances/7038/cmdline
new file mode 100644
index 00000000..6bd011c5
--- /dev/null
+++ b/mock/fixtures/inotify_instances/7038/cmdline
@@ -0,0 +1 @@
+<zombie>
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/7038/fd/0 b/mock/fixtures/inotify_instances/7038/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/7038/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/7038/fd/1 b/mock/fixtures/inotify_instances/7038/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/7038/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/7038/status b/mock/fixtures/inotify_instances/7038/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/7038/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/727/cmdline b/mock/fixtures/inotify_instances/727/cmdline
new file mode 100755
index 00000000..da63c749
Binary files /dev/null and b/mock/fixtures/inotify_instances/727/cmdline differ
diff --git a/mock/fixtures/inotify_instances/727/fd/0 b/mock/fixtures/inotify_instances/727/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/727/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/727/fd/1 b/mock/fixtures/inotify_instances/727/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/727/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/727/fd/14 b/mock/fixtures/inotify_instances/727/fd/14
new file mode 120000
index 00000000..0a39b5fd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/727/fd/14
@@ -0,0 +1 @@
+anon_inode:inotify
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/727/status b/mock/fixtures/inotify_instances/727/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/727/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/728/cmdline b/mock/fixtures/inotify_instances/728/cmdline
new file mode 100755
index 00000000..a76e61c2
Binary files /dev/null and b/mock/fixtures/inotify_instances/728/cmdline differ
diff --git a/mock/fixtures/inotify_instances/728/fd/0 b/mock/fixtures/inotify_instances/728/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/728/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/728/fd/1 b/mock/fixtures/inotify_instances/728/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/728/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/728/status b/mock/fixtures/inotify_instances/728/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/728/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/731/cmdline b/mock/fixtures/inotify_instances/731/cmdline
new file mode 100755
index 00000000..6dd7905c
Binary files /dev/null and b/mock/fixtures/inotify_instances/731/cmdline differ
diff --git a/mock/fixtures/inotify_instances/731/fd/0 b/mock/fixtures/inotify_instances/731/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/731/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/731/fd/1 b/mock/fixtures/inotify_instances/731/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/731/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/731/fd/56 b/mock/fixtures/inotify_instances/731/fd/56
new file mode 120000
index 00000000..0a39b5fd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/731/fd/56
@@ -0,0 +1 @@
+anon_inode:inotify
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/731/status b/mock/fixtures/inotify_instances/731/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/731/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/944/cmdline b/mock/fixtures/inotify_instances/944/cmdline
new file mode 100755
index 00000000..9b0723e5
Binary files /dev/null and b/mock/fixtures/inotify_instances/944/cmdline differ
diff --git a/mock/fixtures/inotify_instances/944/fd/0 b/mock/fixtures/inotify_instances/944/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/944/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/944/fd/1 b/mock/fixtures/inotify_instances/944/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/944/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/944/status b/mock/fixtures/inotify_instances/944/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/944/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/946/cmdline b/mock/fixtures/inotify_instances/946/cmdline
new file mode 100755
index 00000000..2f11ae8d
Binary files /dev/null and b/mock/fixtures/inotify_instances/946/cmdline differ
diff --git a/mock/fixtures/inotify_instances/946/fd/0 b/mock/fixtures/inotify_instances/946/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/946/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/946/fd/1 b/mock/fixtures/inotify_instances/946/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/946/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/946/status b/mock/fixtures/inotify_instances/946/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/946/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/self/cmdline b/mock/fixtures/inotify_instances/self/cmdline
new file mode 100755
index 00000000..b424652e
--- /dev/null
+++ b/mock/fixtures/inotify_instances/self/cmdline
@@ -0,0 +1 @@
+/usr/local/bin/procmock
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/self/fd/0 b/mock/fixtures/inotify_instances/self/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/self/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/self/fd/1 b/mock/fixtures/inotify_instances/self/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/self/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/self/status b/mock/fixtures/inotify_instances/self/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/self/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/mock/fixtures/inotify_instances/thread-self/cmdline b/mock/fixtures/inotify_instances/thread-self/cmdline
new file mode 100755
index 00000000..b424652e
--- /dev/null
+++ b/mock/fixtures/inotify_instances/thread-self/cmdline
@@ -0,0 +1 @@
+/usr/local/bin/procmock
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/thread-self/fd/0 b/mock/fixtures/inotify_instances/thread-self/fd/0
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/thread-self/fd/0
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/thread-self/fd/1 b/mock/fixtures/inotify_instances/thread-self/fd/1
new file mode 120000
index 00000000..dc1dc0cd
--- /dev/null
+++ b/mock/fixtures/inotify_instances/thread-self/fd/1
@@ -0,0 +1 @@
+/dev/null
\ No newline at end of file
diff --git a/mock/fixtures/inotify_instances/thread-self/status b/mock/fixtures/inotify_instances/thread-self/status
new file mode 100644
index 00000000..2c38b7eb
--- /dev/null
+++ b/mock/fixtures/inotify_instances/thread-self/status
@@ -0,0 +1,2 @@
+Uid:	0	0	0	0
+Gid:	0	0	0	0
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 00000000..177706f3
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,29 @@
+[project]
+name = "node-exporter-textfile-collector-scripts"
+version = "0.0.0"
+description = "Metric generators for use with the Prometheus Node Exporter textfile collector."
+readme = "README.md"
+license = {file = "LICENSE"}
+
+requires-python = ">=3.5,<4.0"
+dependencies = [
+    "prometheus_client",
+]
+
+[project.optional-dependencies]
+test = [
+    "pytest",
+    "pytest-golden",
+]
+
+[tool.pytest.ini_options]
+pythonpath = "."
+testpaths = "tests"
+norecursedirs = [
+    ".vscode",
+    ".github",
+    ".circleci",
+    ".pytest_cache",
+    "__pycache__",
+]
+enable_assertion_pass_hook = true
diff --git a/tests/inotify_instances/test__get_processes.yml b/tests/inotify_instances/test__get_processes.yml
new file mode 100644
index 00000000..ec3deb00
--- /dev/null
+++ b/tests/inotify_instances/test__get_processes.yml
@@ -0,0 +1,21 @@
+output:
+  - Process(pid=1, uid=0, command='init', inotify_instances=6)
+  - Process(pid=1016, uid=33, command='dbus-broker-launch', inotify_instances=0)
+  - Process(pid=1017, uid=33, command='dbus-broker', inotify_instances=0)
+  - Process(pid=1024, uid=33, command='rsyslogd', inotify_instances=0)
+  - Process(pid=1025, uid=33, command='polkitd', inotify_instances=0)
+  - Process(pid=1051, uid=33, command='rtkit-daemon', inotify_instances=0)
+  - Process(pid=1189, uid=33, command='at-spi-bus-launcher', inotify_instances=0)
+  - Process(pid=2787, uid=33, command='upowerd', inotify_instances=0)
+  - Process(pid=3376, uid=33, command='keyboxd', inotify_instances=0)
+  - Process(pid=512, uid=33, command='systemd-journald', inotify_instances=6)
+  - Process(pid=547, uid=33, command='systemd-resolved', inotify_instances=0)
+  - Process(pid=548, uid=33, command='systemd-timesyncd', inotify_instances=0)
+  - Process(pid=557, uid=33, command='systemd-udevd', inotify_instances=0)
+  - Process(pid=569, uid=33, command='systemd-networkd', inotify_instances=0)
+  - Process(pid=7038, uid=33, command='<zombie>', inotify_instances=0)
+  - Process(pid=727, uid=33, command='dbus-broker-launch', inotify_instances=1)
+  - Process(pid=728, uid=33, command='dbus-broker', inotify_instances=0)
+  - Process(pid=731, uid=33, command='systemd-logind', inotify_instances=1)
+  - Process(pid=944, uid=33, command='systemd', inotify_instances=0)
+  - Process(pid=946, uid=33, command='(sd-pam)', inotify_instances=0)
diff --git a/tests/inotify_instances/test__pids.yml b/tests/inotify_instances/test__pids.yml
new file mode 100644
index 00000000..3de68698
--- /dev/null
+++ b/tests/inotify_instances/test__pids.yml
@@ -0,0 +1,21 @@
+output:
+- 1
+- 512
+- 547
+- 548
+- 557
+- 569
+- 727
+- 728
+- 731
+- 944
+- 946
+- 1016
+- 1017
+- 1024
+- 1025
+- 1051
+- 1189
+- 2787
+- 3376
+- 7038
diff --git a/tests/inotify_instances/test_generate_process_metrics.yml b/tests/inotify_instances/test_generate_process_metrics.yml
new file mode 100644
index 00000000..e9ef0d0e
--- /dev/null
+++ b/tests/inotify_instances/test_generate_process_metrics.yml
@@ -0,0 +1,7 @@
+output: |
+  # HELP inotify_instances Total number of inotify instances held open by a process.
+  # TYPE inotify_instances gauge
+  inotify_instances{command="init",pid="1",uid="0"} 6.0
+  inotify_instances{command="dbus-broker-launch",pid="727",uid="33"} 1.0
+  inotify_instances{command="systemd-journald",pid="512",uid="33"} 6.0
+  inotify_instances{command="systemd-logind",pid="731",uid="33"} 1.0
diff --git a/tests/inotify_instances/test_generate_process_metrics_command.yml b/tests/inotify_instances/test_generate_process_metrics_command.yml
new file mode 100644
index 00000000..d504812f
--- /dev/null
+++ b/tests/inotify_instances/test_generate_process_metrics_command.yml
@@ -0,0 +1,5 @@
+output: |
+  # HELP inotify_instances Total number of inotify instances held open by a process.
+  # TYPE inotify_instances gauge
+  inotify_instances{command="systemd-journald",pid="512",uid="33"} 6.0
+  inotify_instances{command="systemd-logind",pid="731",uid="33"} 1.0
diff --git a/tests/inotify_instances/test_generate_process_metrics_no_command.yml b/tests/inotify_instances/test_generate_process_metrics_no_command.yml
new file mode 100644
index 00000000..262f65c6
--- /dev/null
+++ b/tests/inotify_instances/test_generate_process_metrics_no_command.yml
@@ -0,0 +1,3 @@
+output: |
+  # HELP inotify_instances Total number of inotify instances held open by a process.
+  # TYPE inotify_instances gauge
diff --git a/tests/inotify_instances/test_generate_process_metrics_no_user.yml b/tests/inotify_instances/test_generate_process_metrics_no_user.yml
new file mode 100644
index 00000000..262f65c6
--- /dev/null
+++ b/tests/inotify_instances/test_generate_process_metrics_no_user.yml
@@ -0,0 +1,3 @@
+output: |
+  # HELP inotify_instances Total number of inotify instances held open by a process.
+  # TYPE inotify_instances gauge
diff --git a/tests/inotify_instances/test_generate_process_metrics_user.yml b/tests/inotify_instances/test_generate_process_metrics_user.yml
new file mode 100644
index 00000000..2926c16b
--- /dev/null
+++ b/tests/inotify_instances/test_generate_process_metrics_user.yml
@@ -0,0 +1,4 @@
+output: |
+  # HELP inotify_instances Total number of inotify instances held open by a process.
+  # TYPE inotify_instances gauge
+  inotify_instances{command="init",pid="1",uid="0"} 6.0
diff --git a/tests/inotify_instances/test_generate_user_metrics.yml b/tests/inotify_instances/test_generate_user_metrics.yml
new file mode 100644
index 00000000..a8c957f7
--- /dev/null
+++ b/tests/inotify_instances/test_generate_user_metrics.yml
@@ -0,0 +1,5 @@
+output: |
+   # HELP inotify_user_instances Total number of inotify instances held open by a user.
+   # TYPE inotify_user_instances gauge
+   inotify_user_instances{uid="0"} 1.0
+   inotify_user_instances{uid="33"} 3.0
diff --git a/tests/inotify_instances/test_generate_user_metrics_no_user.yml b/tests/inotify_instances/test_generate_user_metrics_no_user.yml
new file mode 100644
index 00000000..058acb5b
--- /dev/null
+++ b/tests/inotify_instances/test_generate_user_metrics_no_user.yml
@@ -0,0 +1,3 @@
+output: |
+   # HELP inotify_user_instances Total number of inotify instances held open by a user.
+   # TYPE inotify_user_instances gauge
diff --git a/tests/inotify_instances/test_generate_user_metrics_user.yml b/tests/inotify_instances/test_generate_user_metrics_user.yml
new file mode 100644
index 00000000..459b5376
--- /dev/null
+++ b/tests/inotify_instances/test_generate_user_metrics_user.yml
@@ -0,0 +1,4 @@
+output: |
+   # HELP inotify_user_instances Total number of inotify instances held open by a user.
+   # TYPE inotify_user_instances gauge
+   inotify_user_instances{uid="33"} 3.0
diff --git a/tests/test_inotify_instances.py b/tests/test_inotify_instances.py
new file mode 100644
index 00000000..3b69532a
--- /dev/null
+++ b/tests/test_inotify_instances.py
@@ -0,0 +1,115 @@
+import os
+import re
+
+import pytest
+
+import inotify_instances
+
+
+class StatMock:
+    def __init__(self, uid):
+        self.uid = uid
+
+    def __repr__(self):
+        return f"StatMock(uid={self.uid})"
+
+    def __call__(self, f):
+        pid = os.path.basename(os.path.dirname(f))
+        if pid == "1":
+            # ensure at least one file is not affected by the mock
+            # to generate some diversity
+            return 0
+        return self.uid
+
+
+@pytest.fixture
+def golden(request, golden):
+    return golden.open(f"inotify_instances/{request.node.name}.yml")
+
+
+@pytest.fixture
+def proc():
+    return os.path.abspath(
+        os.path.join(__file__, "..", "..", "mock", "fixtures", "inotify_instances")
+    )
+
+
+@pytest.fixture
+def stat():
+    return StatMock(33)
+
+
+def test__pids(proc, golden):
+    pids = inotify_instances._pids(proc)
+
+    assert sorted(list(pids)) == golden["output"]
+
+
+def test__get_processes(proc, stat, golden):
+    inotify_instances._pid_uid = stat
+    procs = inotify_instances._get_processes(proc)
+
+    assert sorted(map(str, procs)) == golden["output"]
+
+
+def test_generate_process_metrics(proc, stat, golden):
+    inotify_instances._pid_uid = stat
+    command = re.compile(".+")
+    output = inotify_instances._generate_process_metrics(command=command, proc=proc)
+
+    assert output == golden["output"]
+
+
+def test_generate_process_metrics_command(proc, stat, golden):
+    inotify_instances._pid_uid = stat
+    command = re.compile("systemd-.+")
+    output = inotify_instances._generate_process_metrics(command=command, proc=proc)
+
+    assert output == golden["output"]
+
+
+def test_generate_process_metrics_no_command(proc, stat, golden):
+    inotify_instances._pid_uid = stat
+    command = re.compile("prom.+")
+    output = inotify_instances._generate_process_metrics(command=command, proc=proc)
+
+    assert output == golden["output"]
+
+
+def test_generate_process_metrics_user(proc, stat, golden):
+    inotify_instances._pid_uid = stat
+    users = [0]
+    output = inotify_instances._generate_process_metrics(users=users, proc=proc)
+
+    assert output == golden["output"]
+
+
+def test_generate_process_metrics_no_user(proc, stat, golden):
+    inotify_instances._pid_uid = stat
+    users = [42]
+    output = inotify_instances._generate_process_metrics(users=users, proc=proc)
+
+    assert output == golden["output"]
+
+
+def test_generate_user_metrics(proc, stat, golden):
+    inotify_instances._pid_uid = stat
+    output = inotify_instances._generate_user_metrics(proc=proc)
+
+    assert output == golden["output"]
+
+
+def test_generate_user_metrics_user(proc, stat, golden):
+    inotify_instances._pid_uid = stat
+    users = [33]
+    output = inotify_instances._generate_user_metrics(users=users, proc=proc)
+
+    assert output == golden["output"]
+
+
+def test_generate_user_metrics_no_user(proc, stat, golden):
+    inotify_instances._pid_uid = stat
+    users = [42]
+    output = inotify_instances._generate_user_metrics(users=users, proc=proc)
+
+    assert output == golden["output"]