Add tests to make sure that Base.project_names, Base.manifest_names, Base.preferences_names, and Artifacts.artifact_names always have the same length (JuliaLang#40618)

* Add tests to make sure that `Base.project_names`, `Base.manifest_names`, `Base.preferences_names`, and `Artifacts.artifact_names` always have the same length

* Add a comment explaining why we have these tests

Author: DilumAluthge

stdlib/Artifacts/test/runtests.jl

@@ -157,3 +157,10 @@ end
         end
     end
 end
+
+@testset "`Artifacts.artifact_names` and friends" begin
+    n = length(Artifacts.artifact_names)
+    @test length(Base.project_names) == n
+    @test length(Base.manifest_names) == n
+    @test length(Base.preferences_names) == n
+end

test/loading.jl

@@ -718,3 +718,10 @@ import .Foo.Libdl; import Libdl
         end
     end
 end
+
+@testset "`Base.project_names` and friends" begin
+    # Some functions in Pkg assumes that these tuples have the same length
+    n = length(Base.project_names)
+    @test length(Base.manifest_names) == n
+    @test length(Base.preferences_names) == n
+end