Convert `os/mac/diagnostic` test to spec.

Library/Homebrew/test/os/mac/diagnostic_spec.rb

+require "diagnostic"
+
+describe Homebrew::Diagnostic::Checks do
+  specify "#check_for_other_package_managers" do
+    allow(MacOS).to receive(:macports_or_fink).and_return(["fink"])
+    expect(subject.check_for_other_package_managers)
+      .to match("You have MacPorts or Fink installed:")
+  end
+
+  specify "#check_for_unsupported_macos" do
+    ENV.delete("HOMEBREW_DEVELOPER")
+    allow(OS::Mac).to receive(:prerelease?).and_return(true)
+
+    expect(subject.check_for_unsupported_macos)
+      .to match("We do not provide support for this pre-release version.")
+  end
+
+  specify "#check_for_unsupported_curl_vars" do
+    allow(MacOS).to receive(:version).and_return(OS::Mac::Version.new("10.10"))
+    ENV["SSL_CERT_DIR"] = "/some/path"
+
+    expect(subject.check_for_unsupported_curl_vars)
+      .to match("SSL_CERT_DIR support was removed from Apple's curl.")
+  end
+
+  specify "#check_for_beta_xquartz" do
+    allow(MacOS::XQuartz).to receive(:version).and_return("2.7.10_beta2")
+
+    expect(subject.check_for_beta_xquartz)
+      .to match("The following beta release of XQuartz is installed: 2.7.10_beta2")
+  end
+
+  specify "#check_xcode_8_without_clt_on_el_capitan" do
+    allow(MacOS).to receive(:version).and_return(OS::Mac::Version.new("10.11"))
+    allow(MacOS::Xcode).to receive(:installed?).and_return(true)
+    allow(MacOS::Xcode).to receive(:version).and_return("8.0")
+    allow(MacOS::Xcode).to receive(:without_clt?).and_return(true)
+
+    expect(subject.check_xcode_8_without_clt_on_el_capitan)
+      .to match("You have Xcode 8 installed without the CLT")
+  end
+end

Library/Homebrew/test/os/mac/diagnostic_test.rb

-require "testing_env"
-require "fileutils"
-require "pathname"
-require "diagnostic"
-
-class OSMacDiagnosticChecksTest < Homebrew::TestCase
-  def setup
-    super
-    @checks = Homebrew::Diagnostic::Checks.new
-  end
-
-  def test_check_for_other_package_managers
-    MacOS.stubs(:macports_or_fink).returns ["fink"]
-    assert_match "You have MacPorts or Fink installed:",
-      @checks.check_for_other_package_managers
-  end
-
-  def test_check_for_unsupported_macos
-    ENV.delete("HOMEBREW_DEVELOPER")
-    OS::Mac.stubs(:prerelease?).returns true
-    assert_match "We do not provide support for this pre-release version.",
-      @checks.check_for_unsupported_macos
-  end
-
-  def test_check_for_unsupported_curl_vars
-    MacOS.stubs(:version).returns OS::Mac::Version.new("10.10")
-    ENV["SSL_CERT_DIR"] = "/some/path"
-
-    assert_match "SSL_CERT_DIR support was removed from Apple's curl.",
-      @checks.check_for_unsupported_curl_vars
-  end
-
-  def test_check_for_beta_xquartz
-    MacOS::XQuartz.stubs(:version).returns("2.7.10_beta2")
-    assert_match "The following beta release of XQuartz is installed: 2.7.10_beta2", @checks.check_for_beta_xquartz
-  end
-
-  def test_check_xcode_8_without_clt_on_el_capitan
-    MacOS.stubs(:version).returns OS::Mac::Version.new("10.11")
-    MacOS::Xcode.stubs(:installed?).returns true
-    MacOS::Xcode.stubs(:version).returns "8.0"
-    MacOS::Xcode.stubs(:without_clt?).returns true
-    assert_match "You have Xcode 8 installed without the CLT", @checks.check_xcode_8_without_clt_on_el_capitan
-  end
-end