diagnostic: fix paths usage.

- Don't allow taking an argument. This doesn't work and never has as it
  caches the result regardless of the argument.
- Don't rely on the PATH to check for external commands.

1 files changed, 1 insertions, 1 deletions

diff --git a/Library/Homebrew/test/diagnostic_spec.rb b/Library/Homebrew/test/diagnostic_spec.rb
index 8a25413ed..f347010a9 100644
--- a/Library/Homebrew/test/diagnostic_spec.rb
+++ b/Library/Homebrew/test/diagnostic_spec.rb
@@ -194,7 +194,7 @@ describe Homebrew::Diagnostic::Checks do
           FileUtils.chmod 0755, cmd
         end
 
-        ENV["PATH"] = [path1, path2, ENV["PATH"]].join File::PATH_SEPARATOR
+        allow(Tap).to receive(:cmd_directories).and_return([path1, path2])
 
         expect(subject.check_for_external_cmd_name_conflict)
           .to match("brew-foo")