Add some more tests

Library/Homebrew/test/dev-cmd/determine-test-runners_spec.rb

@@ -1,8 +1,67 @@
 # typed: false
 # frozen_string_literal: true
 
+require "dev-cmd/determine-test-runners"
 require "cmd/shared_examples/args_parse"
 
 describe "brew determine-test-runners" do
   it_behaves_like "parseable arguments"
+
+  let(:github_output) { "#{TEST_TMPDIR}/github_output" }
+  let(:runner_env) {
+    {
+      "HOMEBREW_LINUX_RUNNER" => "ubuntu-latest",
+      "HOMEBREW_LINUX_CLEANUP" => "false",
+      "GITHUB_RUN_ID" => "12345",
+      "GITHUB_RUN_ATTEMPT" => "1",
+      "GITHUB_OUTPUT" => github_output,
+    }
+  }
+  # TODO: Generate this dynamically based on our supported macOS versions.
+  let(:all_runners) { ["11", "11-arm64", "12", "12-arm64", "13", "13-arm64", "ubuntu-latest"] }
+
+  after(:each) do
+    FileUtils.rm_f github_output
+  end
+
+  it "fails without any arguments", :integration_test do
+    expect { brew "determine-test-runners" }
+      .to not_to_output.to_stdout
+      .and be_a_failure
+  end
+
+  it "assigns all runners for formulae without any requirements", :integration_test, :needs_linux do
+    setup_test_formula "testball"
+
+    ohai runner_env
+    expect { brew "determine-test-runners", "testball", runner_env }
+      .to not_to_output.to_stdout
+      .and not_to_output.to_stderr
+      .and be_a_success
+
+    expect(File.read(github_output)).not_to be_empty
+    expect(get_runners(github_output)).to eq(all_runners)
+  end
+
+  it "assigns all runners when there are deleted formulae", :integration_test, :needs_linux do
+    expect { brew "determine-test-runners", "", "testball", runner_env }
+      .to not_to_output.to_stdout
+      .and not_to_output.to_stderr
+      .and be_a_success
+
+    expect(File.read(github_output)).not_to be_empty
+    expect(get_runners(github_output)).to eq(all_runners)
+  end
+end
+
+def parse_runner_hash(file)
+  runner_line = File.open(file).first
+  json_text = runner_line[/runners=(.*)/, 1]
+  JSON.parse(json_text)
+end
+
+def get_runners(file)
+  runner_hash = parse_runner_hash(file)
+  runner_hash.map { |item| item["runner"].delete_suffix("-12345-1") }
+             .sort
 end