Fix the dead Test-extension guard in the error hint

Project.toml

@@ -1,6 +1,6 @@
 name = "InverseFunctions"
 uuid = "3587e190-3f89-42d0-90ee-14403ec27112"
-version = "0.1.17"
+version = "0.1.18"
 
 [deps]
 Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"

src/InverseFunctions.jl

@@ -38,7 +38,7 @@ if isdefined(Base, :get_extension) && isdefined(Base.Experimental, :register_err
     function __init__()
         Base.Experimental.register_error_hint(MethodError) do io, exc, _, _
             if exc.f === test_inverse &&
-                (Base.get_extension(InverseFunctions, :InverseFunctionsTest) === nothing)
+                (Base.get_extension(InverseFunctions, :InverseFunctionsTestExt) === nothing)
                 print(io, "\nDid you forget to load Test?")
             end
         end

test/test_inverse.jl

@@ -43,6 +43,33 @@ end
     InverseFunctions.test_inverse(inverse, log, compare = ===)
 end
 
+@testset "test_inverse" begin
+    @test hasmethod(InverseFunctions.test_inverse, Tuple{Any,Any})
+
+    err = try
+        InverseFunctions.test_inverse(identity)
+    catch e
+        e
+    end
+    @test err isa MethodError
+    @test !occursin("Did you forget to load Test?", sprint(showerror, err))
+
+    # Test can't be unloaded, so the behaviour without it is checked in a subprocess
+    if isdefined(Base, :get_extension)
+        script = """
+            using InverseFunctions
+            println("hasmethod: ", hasmethod(InverseFunctions.test_inverse, Tuple{Any,Any}))
+            InverseFunctions.test_inverse(identity, 1)
+            """
+        cmd = `$(Base.julia_cmd()) --startup-file=no --project=$(Base.active_project()) -e $script`
+        output = IOBuffer()
+        run(pipeline(ignorestatus(cmd); stdout=output, stderr=output))
+        str = String(take!(output))
+        @test occursin("hasmethod: false", str)
+        @test occursin("Did you forget to load Test?", str)
+    end
+end
+
 @testset "maths" begin
     InverseFunctions.test_inverse(!, false)