diff --git a/Library/Homebrew/cmd/untap.rb b/Library/Homebrew/cmd/untap.rb
index f2a2547d41..17c5c11af6 100644
--- a/Library/Homebrew/cmd/untap.rb
+++ b/Library/Homebrew/cmd/untap.rb
@@ -2,11 +2,10 @@
 # frozen_string_literal: true
 
 require "abstract_command"
-require "untap"
 
 module Homebrew
   module Cmd
-    class UntapCmd < AbstractCommand
+    class Untap < AbstractCommand
       cmd_args do
         description <<~EOS
           Remove a tapped formula repository.
@@ -23,8 +22,8 @@ module Homebrew
           odie "Untapping #{tap} is not allowed" if tap.core_tap? && Homebrew::EnvConfig.no_install_from_api?
 
           if Homebrew::EnvConfig.no_install_from_api? || (!tap.core_tap? && !tap.core_cask_tap?)
-            installed_tap_formulae = Untap.installed_formulae_for(tap:)
-            installed_tap_casks = Untap.installed_casks_for(tap:)
+            installed_tap_formulae = installed_formulae_for(tap:)
+            installed_tap_casks = installed_casks_for(tap:)
 
             if installed_tap_formulae.present? || installed_tap_casks.present?
               installed_names = (installed_tap_formulae + installed_tap_casks.map(&:token)).join("\n")
@@ -45,6 +44,54 @@ module Homebrew
           tap.uninstall manual: true
         end
       end
+
+      # All installed formulae currently available in a tap by formula full name.
+      sig { params(tap: Tap).returns(T::Array[Formula]) }
+      def installed_formulae_for(tap:)
+        tap.formula_names.filter_map do |formula_name|
+          next unless installed_formulae_names.include?(T.must(formula_name.split("/").last))
+
+          formula = begin
+            Formulary.factory(formula_name)
+          rescue FormulaUnavailableError
+            # Don't blow up because of a single unavailable formula.
+            next
+          end
+
+          # Can't use Formula#any_version_installed? because it doesn't consider
+          # taps correctly.
+          formula if formula.installed_kegs.any? { |keg| keg.tab.tap == tap }
+        end
+      end
+
+      # All installed casks currently available in a tap by cask full name.
+      sig { params(tap: Tap).returns(T::Array[Cask::Cask]) }
+      def installed_casks_for(tap:)
+        tap.cask_tokens.filter_map do |cask_token|
+          next unless installed_cask_tokens.include?(T.must(cask_token.split("/").last))
+
+          cask = begin
+            Cask::CaskLoader.load(cask_token)
+          rescue Cask::CaskUnavailableError
+            # Don't blow up because of a single unavailable cask.
+            next
+          end
+
+          cask if cask.installed?
+        end
+      end
+
+      private
+
+      sig { returns(T::Set[String]) }
+      def installed_formulae_names
+        @installed_formulae_names ||= T.let(Formula.installed_formula_names.to_set.freeze, T.nilable(T::Set[String]))
+      end
+
+      sig { returns(T::Set[String]) }
+      def installed_cask_tokens
+        @installed_cask_tokens ||= T.let(Cask::Caskroom.tokens.to_set.freeze, T.nilable(T::Set[String]))
+      end
     end
   end
 end
diff --git a/Library/Homebrew/test/cmd/untap_spec.rb b/Library/Homebrew/test/cmd/untap_spec.rb
index ba9bb56ec4..bc5d286724 100644
--- a/Library/Homebrew/test/cmd/untap_spec.rb
+++ b/Library/Homebrew/test/cmd/untap_spec.rb
@@ -3,7 +3,9 @@
 require "cmd/shared_examples/args_parse"
 require "cmd/untap"
 
-RSpec.describe Homebrew::Cmd::UntapCmd do
+RSpec.describe Homebrew::Cmd::Untap do
+  let(:class_instance) { described_class.new(%w[arg1]) }
+
   it_behaves_like "parseable arguments"
 
   it "untaps a given Tap", :integration_test do
@@ -14,4 +16,125 @@ RSpec.describe Homebrew::Cmd::UntapCmd do
       .and not_to_output.to_stdout
       .and be_a_success
   end
+
+  describe "#installed_formulae_for", :integration_test do
+    shared_examples "finds installed formulae in tap" do
+      def load_formula(name:, with_formula_file: false, mock_install: false)
+        formula = if with_formula_file
+          path = setup_test_formula(name, tap:)
+          Formulary.factory(path)
+        else
+          formula(name, tap:) do
+            url "https://brew.sh/#{name}-1.0.tgz"
+          end
+        end
+
+        if mock_install
+          keg_path = HOMEBREW_CELLAR/name/"1.2.3"
+          keg_path.mkpath
+
+          tab_path = keg_path/Tab::FILENAME
+          tab_path.write <<~JSON
+            {
+              "source": {
+                "tap": "#{tap}"
+              }
+            }
+          JSON
+        end
+
+        formula
+      end
+
+      let!(:currently_installed_formula) do
+        load_formula(name: "current_install", with_formula_file: true, mock_install: true)
+      end
+
+      before do
+        # Formula that is available from a tap but not installed.
+        load_formula(name: "no_install", with_formula_file: true)
+
+        # Formula that was installed from a tap but is no longer available from that tap.
+        load_formula(name: "legacy_install", mock_install: true)
+
+        tap.clear_cache
+      end
+
+      it "returns the expected formulae" do
+        expect(class_instance.installed_formulae_for(tap:).map(&:full_name))
+          .to eq([currently_installed_formula.full_name])
+      end
+    end
+
+    context "with core tap" do
+      let(:tap) { CoreTap.instance }
+
+      include_examples "finds installed formulae in tap"
+    end
+
+    context "with non-core tap" do
+      let(:tap) { Tap.fetch("homebrew", "foo") }
+
+      before do
+        tap.formula_dir.mkpath
+      end
+
+      include_examples "finds installed formulae in tap"
+    end
+  end
+
+  describe "#installed_casks_for", :cask do
+    shared_examples "finds installed casks in tap" do
+      def load_cask(token:, with_cask_file: false, mock_install: false)
+        cask_loader = Cask::CaskLoader::FromContentLoader.new(<<~RUBY, tap:)
+          cask '#{token}' do
+            version "1.2.3"
+            sha256 :no_check
+
+            url 'https://brew.sh/'
+          end
+        RUBY
+
+        cask = cask_loader.load(config: nil)
+
+        if with_cask_file
+          cask_path = tap.cask_dir/"#{token}.rb"
+          cask_path.parent.mkpath
+          cask_path.write cask.source
+        end
+
+        InstallHelper.install_with_caskfile(cask) if mock_install
+
+        cask
+      end
+
+      let!(:currently_installed_cask) do
+        load_cask(token: "current_install", with_cask_file: true, mock_install: true)
+      end
+
+      before do
+        # Cask that is available from a tap but not installed.
+        load_cask(token: "no_install", with_cask_file: true)
+
+        # Cask that was installed from a tap but is no longer available from that tap.
+        load_cask(token: "legacy_install", mock_install: true)
+      end
+
+      it "returns the expected casks" do
+        expect(class_instance.installed_casks_for(tap:)).to eq([currently_installed_cask])
+      end
+    end
+
+    context "with core cask tap" do
+      let(:tap) { CoreCaskTap.instance }
+
+      include_examples "finds installed casks in tap"
+    end
+
+    context "with non-core cask tap" do
+      let(:tap) { Tap.fetch("homebrew", "foo") }
+
+      include_examples "finds installed casks in tap"
+    end
+  end
 end
diff --git a/Library/Homebrew/test/untap_spec.rb b/Library/Homebrew/test/untap_spec.rb
deleted file mode 100644
index e88f3d27f6..0000000000
--- a/Library/Homebrew/test/untap_spec.rb
+++ /dev/null
@@ -1,126 +0,0 @@
-# frozen_string_literal: true
-
-require "untap"
-
-RSpec.describe Homebrew::Untap do
-  describe ".installed_formulae_for", :integration_test do
-    shared_examples "finds installed formulae in tap" do
-      def load_formula(name:, with_formula_file: false, mock_install: false)
-        formula = if with_formula_file
-          path = setup_test_formula(name, tap:)
-          Formulary.factory(path)
-        else
-          formula(name, tap:) do
-            url "https://brew.sh/#{name}-1.0.tgz"
-          end
-        end
-
-        if mock_install
-          keg_path = HOMEBREW_CELLAR/name/"1.2.3"
-          keg_path.mkpath
-
-          tab_path = keg_path/Tab::FILENAME
-          tab_path.write <<~JSON
-            {
-              "source": {
-                "tap": "#{tap}"
-              }
-            }
-          JSON
-        end
-
-        formula
-      end
-
-      let!(:currently_installed_formula) do
-        load_formula(name: "current_install", with_formula_file: true, mock_install: true)
-      end
-
-      before do
-        # Formula that is available from a tap but not installed.
-        load_formula(name: "no_install", with_formula_file: true)
-
-        # Formula that was installed from a tap but is no longer available from that tap.
-        load_formula(name: "legacy_install", mock_install: true)
-
-        tap.clear_cache
-      end
-
-      it "returns the expected formulae" do
-        expect(described_class.installed_formulae_for(tap:).map(&:full_name))
-          .to eq([currently_installed_formula.full_name])
-      end
-    end
-
-    context "with core tap" do
-      let(:tap) { CoreTap.instance }
-
-      include_examples "finds installed formulae in tap"
-    end
-
-    context "with non-core tap" do
-      let(:tap) { Tap.fetch("homebrew", "foo") }
-
-      before do
-        tap.formula_dir.mkpath
-      end
-
-      include_examples "finds installed formulae in tap"
-    end
-  end
-
-  describe ".installed_casks_for", :cask do
-    shared_examples "finds installed casks in tap" do
-      def load_cask(token:, with_cask_file: false, mock_install: false)
-        cask_loader = Cask::CaskLoader::FromContentLoader.new(<<~RUBY, tap:)
-          cask '#{token}' do
-            version "1.2.3"
-            sha256 :no_check
-
-            url 'https://brew.sh/'
-          end
-        RUBY
-
-        cask = cask_loader.load(config: nil)
-
-        if with_cask_file
-          cask_path = tap.cask_dir/"#{token}.rb"
-          cask_path.parent.mkpath
-          cask_path.write cask.source
-        end
-
-        InstallHelper.install_with_caskfile(cask) if mock_install
-
-        cask
-      end
-
-      let!(:currently_installed_cask) do
-        load_cask(token: "current_install", with_cask_file: true, mock_install: true)
-      end
-
-      before do
-        # Cask that is available from a tap but not installed.
-        load_cask(token: "no_install", with_cask_file: true)
-
-        # Cask that was installed from a tap but is no longer available from that tap.
-        load_cask(token: "legacy_install", mock_install: true)
-      end
-
-      it "returns the expected casks" do
-        expect(described_class.installed_casks_for(tap:)).to eq([currently_installed_cask])
-      end
-    end
-
-    context "with core cask tap" do
-      let(:tap) { CoreCaskTap.instance }
-
-      include_examples "finds installed casks in tap"
-    end
-
-    context "with non-core cask tap" do
-      let(:tap) { Tap.fetch("homebrew", "foo") }
-
-      include_examples "finds installed casks in tap"
-    end
-  end
-end
diff --git a/Library/Homebrew/untap.rb b/Library/Homebrew/untap.rb
deleted file mode 100644
index 3a856f2a91..0000000000
--- a/Library/Homebrew/untap.rb
+++ /dev/null
@@ -1,60 +0,0 @@
-# typed: true
-# frozen_string_literal: true
-
-require "extend/cachable"
-
-module Homebrew
-  # Helpers for the `brew untap` command.
-  # @api private
-  module Untap
-    extend Cachable
-
-    # All installed formulae currently available in a tap by formula full name.
-    sig { params(tap: Tap).returns(T::Array[Formula]) }
-    def self.installed_formulae_for(tap:)
-      tap.formula_names.filter_map do |formula_name|
-        next unless installed_formulae_names.include?(T.must(formula_name.split("/").last))
-
-        formula = begin
-          Formulary.factory(formula_name)
-        rescue FormulaUnavailableError
-          # Don't blow up because of a single unavailable formula.
-          next
-        end
-
-        # Can't use Formula#any_version_installed? because it doesn't consider
-        # taps correctly.
-        formula if formula.installed_kegs.any? { |keg| keg.tab.tap == tap }
-      end
-    end
-
-    sig { returns(T::Set[String]) }
-    def self.installed_formulae_names
-      cache[:installed_formulae_names] ||= Formula.installed_formula_names.to_set.freeze
-    end
-    private_class_method :installed_formulae_names
-
-    # All installed casks currently available in a tap by cask full name.
-    sig { params(tap: Tap).returns(T::Array[Cask::Cask]) }
-    def self.installed_casks_for(tap:)
-      tap.cask_tokens.filter_map do |cask_token|
-        next unless installed_cask_tokens.include?(T.must(cask_token.split("/").last))
-
-        cask = begin
-          Cask::CaskLoader.load(cask_token)
-        rescue Cask::CaskUnavailableError
-          # Don't blow up because of a single unavailable cask.
-          next
-        end
-
-        cask if cask.installed?
-      end
-    end
-
-    sig { returns(T::Set[String]) }
-    def self.installed_cask_tokens
-      cache[:installed_cask_tokens] ||= Cask::Caskroom.tokens.to_set.freeze
-    end
-    private_class_method :installed_cask_tokens
-  end
-end