diff --git a/Library/Homebrew/github_runner_matrix.rb b/Library/Homebrew/github_runner_matrix.rb
index 3c013423b5..1a86aa7942 100644
--- a/Library/Homebrew/github_runner_matrix.rb
+++ b/Library/Homebrew/github_runner_matrix.rb
@@ -255,17 +255,10 @@ class GitHubRunnerMatrix
       @testing_formulae.select do |formula|
         next false if macos_version && !formula.compatible_with?(macos_version)
 
-        simulate_arch = case arch
-        when :x86_64
-          :intel
-        when :arm64
-          :arm
-        else
-          :dunno
-        end
-        Homebrew::SimulateSystem.with(os: platform, arch: simulate_arch) do
-          formula.public_send(:"#{platform}_compatible?") &&
-            formula.public_send(:"#{arch}_compatible?")
+        Homebrew::SimulateSystem.with(os: platform, arch: Homebrew::SimulateSystem.arch_symbols.fetch(arch)) do
+          simulated_formula = TestRunnerFormula.new(Formulary.factory(formula.name))
+          simulated_formula.public_send(:"#{platform}_compatible?") &&
+            simulated_formula.public_send(:"#{arch}_compatible?")
         end
       end
     end
@@ -283,8 +276,11 @@ class GitHubRunnerMatrix
                                        .select do |dependent_f|
           next false if macos_version && !dependent_f.compatible_with?(macos_version)
 
-          dependent_f.public_send(:"#{platform}_compatible?") &&
-            dependent_f.public_send(:"#{arch}_compatible?")
+          Homebrew::SimulateSystem.with(os: platform, arch: Homebrew::SimulateSystem.arch_symbols.fetch(arch)) do
+            simulated_dependent_f = TestRunnerFormula.new(Formulary.factory(dependent_f.name))
+            simulated_dependent_f.public_send(:"#{platform}_compatible?") &&
+              simulated_dependent_f.public_send(:"#{arch}_compatible?")
+          end
         end
 
         # These arrays will generally have been generated by different Formulary caches,
diff --git a/Library/Homebrew/simulate_system.rb b/Library/Homebrew/simulate_system.rb
index e40d891581..840d4ea963 100644
--- a/Library/Homebrew/simulate_system.rb
+++ b/Library/Homebrew/simulate_system.rb
@@ -10,6 +10,11 @@ module Homebrew
     class << self
       attr_reader :arch, :os
 
+      sig { returns(T::Hash[Symbol, Symbol]) }
+      def arch_symbols
+        { arm64: :arm, x86_64: :intel }.freeze
+      end
+
       sig {
         type_parameters(:U).params(
           os:     Symbol,
diff --git a/Library/Homebrew/test/github_runner_matrix_spec.rb b/Library/Homebrew/test/github_runner_matrix_spec.rb
index 7379e0d7d9..8e062d9aa2 100644
--- a/Library/Homebrew/test/github_runner_matrix_spec.rb
+++ b/Library/Homebrew/test/github_runner_matrix_spec.rb
@@ -20,7 +20,7 @@ RSpec.describe GitHubRunnerMatrix, :no_api do
     MacOSVersion::SYMBOLS.find { |k, _| k == described_class::NEWEST_HOMEBREW_CORE_MACOS_RUNNER }
   end
 
-  let(:testball) { TestRunnerFormula.new(Testball.new) }
+  let(:testball) { setup_test_runner_formula("testball") }
   let(:testball_depender) { setup_test_runner_formula("testball-depender", ["testball"]) }
   let(:testball_depender_linux) { setup_test_runner_formula("testball-depender-linux", ["testball", :linux]) }
   let(:testball_depender_macos) { setup_test_runner_formula("testball-depender-macos", ["testball", :macos]) }
@@ -315,6 +315,7 @@ RSpec.describe GitHubRunnerMatrix, :no_api do
       end
     end
 
+    stub_formula_loader f
     TestRunnerFormula.new(f)
   end
 end
diff --git a/Library/Homebrew/test_runner_formula.rb b/Library/Homebrew/test_runner_formula.rb
index e3c3c987d6..34c617d77f 100644
--- a/Library/Homebrew/test_runner_formula.rb
+++ b/Library/Homebrew/test_runner_formula.rb
@@ -77,8 +77,6 @@ class TestRunnerFormula
     macos_version.public_send(requirement.comparator, requirement.version)
   end
 
-  SIMULATE_SYSTEM_SYMBOLS = T.let({ arm64: :arm, x86_64: :intel }.freeze, T::Hash[Symbol, Symbol])
-
   sig {
     params(
       platform:      Symbol,
@@ -98,7 +96,7 @@ class TestRunnerFormula
 
       with_env(HOMEBREW_EVAL_ALL: eval_all_env) do
         os = macos_version || platform
-        arch = SIMULATE_SYSTEM_SYMBOLS.fetch(arch)
+        arch = Homebrew::SimulateSystem.arch_symbols.fetch(arch)
 
         Homebrew::SimulateSystem.with(os:, arch:) do
           Formula.public_send(formula_selector)