add test

Library/Homebrew/test/rubocops/lines_spec.rb

@@ -58,3 +58,75 @@ describe RuboCop::Cop::FormulaAudit::Lines do
     end
   end
 end
+
+describe RuboCop::Cop::FormulaAudit::GenerateCompletionsDSL do
+  subject(:cop) { described_class.new }
+
+  it "reports an offense when writing to a shell completions file directly" do
+    expect_offense(<<~RUBY)
+      class Foo < Formula
+        name "foo"
+
+        def install
+          (bash_completion/"foo").write Utils.safe_popen_read(bin/"foo", "completions", "bash")
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `generate_completions_from_executable(bin/"foo", "completions", shells: [:bash])` instead of `(bash_completion/"foo").write Utils.safe_popen_read(bin/"foo", "completions", "bash")`.
+        end
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      class Foo < Formula
+        name "foo"
+
+        def install
+          generate_completions_from_executable(bin/"foo", "completions", shells: [:bash])
+        end
+      end
+    RUBY
+  end
+
+  it "reports an offense when writing to a completions file indirectly" do
+    expect_offense(<<~RUBY)
+      class Foo < Formula
+        name "foo"
+
+        def install
+          output = Utils.safe_popen_read(bin/"foo", "completions", "bash")
+          (bash_completion/"foo").write output
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `generate_completions_from_executable` DSL instead of `(bash_completion/"foo").write output`.
+        end
+      end
+    RUBY
+  end
+end
+
+describe RuboCop::Cop::FormulaAudit::SingleGenerateCompletionsDSLCall do
+  subject(:cop) { described_class.new }
+
+  it "reports an offense when using multiple #generate_completions_from_executable calls for different shells" do
+    expect_offense(<<~RUBY)
+      class Foo < Formula
+        name "foo"
+
+        def install
+          generate_completions_from_executable(bin/"foo", "completions", shells: [:bash])
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use a single `generate_completions_from_executable` call combining all specified shells.
+          generate_completions_from_executable(bin/"foo", "completions", shells: [:zsh])
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use a single `generate_completions_from_executable` call combining all specified shells.
+          generate_completions_from_executable(bin/"foo", "completions", shells: [:fish])
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `generate_completions_from_executable(bin/"foo", "completions")` instead of `generate_completions_from_executable(bin/"foo", "completions", shells: [:fish])`.
+        end
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      class Foo < Formula
+        name "foo"
+
+        def install
+          generate_completions_from_executable(bin/"foo", "completions")
+        end
+      end
+    RUBY
+  end
+end