Stop bundle specs leaking Tap and Cask doubles

- `Homebrew::Bundle::Tap.taps` and `Homebrew::Bundle::Cask.casks`
  memoise whatever `Tap.select` and `Cask::Caskroom.casks` return, so
  the `instance_double`s stubbed in `tap_spec` and `dumper_spec`
  survived into later examples.
- `npm_spec`'s `Installer.install!` example then hit rspec-mocks'
  "leaked into another example" error whenever a dumper example ran
  first in the same process, failing random test orders.

Signed-off-by: Patrick Linnane <patrick@linnane.io>

Library/Homebrew/test/bundle/dumper_spec.rb

@@ -47,6 +47,12 @@ RSpec.describe Homebrew::Bundle::Dumper do
     allow(Tap).to receive(:select).and_return([])
   end
 
+  # `Tap.taps` and `Cask.casks` memoise the stubbed doubles, which must not outlive the example.
+  after do
+    Homebrew::Bundle::Tap.reset!
+    Homebrew::Bundle::Cask.reset!
+  end
+
   it "generates output" do
     expect(dumper.build_brewfile(
              describe: false, no_restart: false, formulae: true, taps: true, casks: true,

Library/Homebrew/test/bundle/tap_spec.rb

@@ -6,6 +6,11 @@ require "bundle/skipper"
 require "bundle/tap"
 
 RSpec.describe Homebrew::Bundle::Tap do
+  # `taps` memoises the stubbed `Tap` doubles, which must not outlive the example.
+  after do
+    described_class.reset!
+  end
+
   describe "dumping" do
     subject(:dumper) { described_class }