diff --git a/android/fixture.go b/android/fixture.go
index 3f01f5a..c2b16f6 100644
--- a/android/fixture.go
+++ b/android/fixture.go
@@ -213,6 +213,46 @@
 	})
 }
 
+// FixtureTestRunner determines the type of test to run.
+//
+// If no custom FixtureTestRunner is provided (using the FixtureSetTestRunner) then the default test
+// runner will run a standard Soong test that corresponds to what happens when Soong is run on the
+// command line.
+type FixtureTestRunner interface {
+	// FinalPreparer is a function that is run immediately before parsing the blueprint files. It is
+	// intended to perform the initialization needed by PostParseProcessor.
+	//
+	// It returns a CustomTestResult that is passed into PostParseProcessor and returned from
+	// FixturePreparer.RunTestWithCustomResult. If it needs to return some custom data then it must
+	// provide its own implementation of CustomTestResult and return an instance of that. Otherwise,
+	// it can just return the supplied *TestResult.
+	FinalPreparer(result *TestResult) CustomTestResult
+
+	// PostParseProcessor is called after successfully parsing the blueprint files and can do further
+	// work on the result of parsing the files.
+	//
+	// Successfully parsing simply means that no errors were encountered when parsing the blueprint
+	// files.
+	//
+	// This must collate any information useful for testing, e.g. errs, ninja deps and custom data in
+	// the supplied result.
+	PostParseProcessor(result CustomTestResult)
+}
+
+// FixtureSetTestRunner sets the FixtureTestRunner in the fixture.
+//
+// It is an error if more than one of these is applied to a single fixture. If none of these are
+// applied then the fixture will use the defaultTestRunner which will run the test as if it was
+// being run in `m <target>`.
+func FixtureSetTestRunner(testRunner FixtureTestRunner) FixturePreparer {
+	return newSimpleFixturePreparer(func(fixture *fixture) {
+		if fixture.testRunner != nil {
+			panic("fixture test runner has already been set")
+		}
+		fixture.testRunner = testRunner
+	})
+}
+
 // Modify the config
 func FixtureModifyConfig(mutator func(config Config)) FixturePreparer {
 	return newSimpleFixturePreparer(func(f *fixture) {
@@ -391,6 +431,21 @@
 	// Shorthand for Fixture(t).RunTest()
 	RunTest(t *testing.T) *TestResult
 
+	// RunTestWithCustomResult runs the test just as RunTest(t) does but instead of returning a
+	// *TestResult it returns the CustomTestResult that was returned by the custom
+	// FixtureTestRunner.PostParseProcessor method that ran the test, or the *TestResult if that
+	// method returned nil.
+	//
+	// This method must be used when needing to access custom data collected by the
+	// FixtureTestRunner.PostParseProcessor method.
+	//
+	// e.g. something like this
+	//
+	//   preparers := ...FixtureSetTestRunner(&myTestRunner)...
+	//   customResult := preparers.RunTestWithCustomResult(t).(*myCustomTestResult)
+	//   doSomething(customResult.data)
+	RunTestWithCustomResult(t *testing.T) CustomTestResult
+
 	// Run the test with the supplied Android.bp file.
 	//
 	// preparer.RunTestWithBp(t, bp) is shorthand for
@@ -619,7 +674,7 @@
 	MockFS() MockFS
 
 	// Run the test, checking any errors reported and returning a TestResult instance.
-	RunTest() *TestResult
+	RunTest() CustomTestResult
 }
 
 // Struct to allow TestResult to embed a *TestContext and allow call forwarding to its methods.
@@ -642,6 +697,39 @@
 	NinjaDeps []string
 }
 
+func (r *TestResult) testResult() *TestResult { return r }
+
+// CustomTestResult is the interface that FixtureTestRunner implementations who wish to return
+// custom data must implement. It must embed *TestResult and initialize that to the value passed
+// into the method. It is returned from the FixtureTestRunner.FinalPreparer, passed into the
+// FixtureTestRunner.PostParseProcessor and returned from FixturePreparer.RunTestWithCustomResult.
+//
+// e.g. something like this:
+//
+//		type myCustomTestResult struct {
+//		    *android.TestResult
+//		    data []string
+//		}
+//
+//		func (r *myTestRunner) FinalPreparer(result *TestResult) CustomTestResult {
+//	     ... do some final test preparation ...
+//	     return &myCustomTestResult{TestResult: result)
+//	 }
+//
+//		func (r *myTestRunner) PostParseProcessor(result CustomTestResult) {
+//		    ...
+//		    myData := []string {....}
+//		    ...
+//		    customResult := result.(*myCustomTestResult)
+//	     customResult.data = myData
+//		}
+type CustomTestResult interface {
+	// testResult returns the embedded *TestResult.
+	testResult() *TestResult
+}
+
+var _ CustomTestResult = (*TestResult)(nil)
+
 type TestPathContext struct {
 	*TestResult
 }
@@ -696,6 +784,11 @@
 
 func (b *baseFixturePreparer) RunTest(t *testing.T) *TestResult {
 	t.Helper()
+	return b.RunTestWithCustomResult(t).testResult()
+}
+
+func (b *baseFixturePreparer) RunTestWithCustomResult(t *testing.T) CustomTestResult {
+	t.Helper()
 	fixture := b.self.Fixture(t)
 	return fixture.RunTest()
 }
@@ -724,13 +817,16 @@
 		ctx.SetModuleListFile(ctx.config.mockBpList)
 	}
 
-	return fixture.RunTest()
+	return fixture.RunTest().testResult()
 }
 
 type fixture struct {
 	// The preparers used to create this fixture.
 	preparers []*simpleFixturePreparer
 
+	// The test runner used in this fixture, defaults to defaultTestRunner if not set.
+	testRunner FixtureTestRunner
+
 	// The gotest state of the go test within which this was created.
 	t *testing.T
 
@@ -762,7 +858,7 @@
 	return f.mockFS
 }
 
-func (f *fixture) RunTest() *TestResult {
+func (f *fixture) RunTest() CustomTestResult {
 	f.t.Helper()
 
 	// If in debug mode output the state of the fixture before running the test.
@@ -800,30 +896,59 @@
 	// Set the NameResolver in the TestContext.
 	ctx.NameResolver = resolver
 
-	ctx.Register()
-	var ninjaDeps []string
-	extraNinjaDeps, errs := ctx.ParseBlueprintsFiles("ignored")
-	if len(errs) == 0 {
-		ninjaDeps = append(ninjaDeps, extraNinjaDeps...)
-		extraNinjaDeps, errs = ctx.PrepareBuildActions(f.config)
-		if len(errs) == 0 {
-			ninjaDeps = append(ninjaDeps, extraNinjaDeps...)
-		}
+	// If test runner has not been set then use the default runner.
+	if f.testRunner == nil {
+		f.testRunner = defaultTestRunner
 	}
 
+	// Create the result to collate result information.
 	result := &TestResult{
 		testContext: testContext{ctx},
 		fixture:     f,
 		Config:      f.config,
-		Errs:        errs,
-		NinjaDeps:   ninjaDeps,
+	}
+
+	// Do any last minute preparation before parsing the blueprint files.
+	customResult := f.testRunner.FinalPreparer(result)
+
+	// Parse the blueprint files adding the information to the result.
+	extraNinjaDeps, errs := ctx.ParseBlueprintsFiles("ignored")
+	result.NinjaDeps = append(result.NinjaDeps, extraNinjaDeps...)
+	result.Errs = append(result.Errs, errs...)
+
+	if len(result.Errs) == 0 {
+		// If parsing the blueprint files was successful then perform any additional processing.
+		f.testRunner.PostParseProcessor(customResult)
 	}
 
 	f.errorHandler.CheckErrors(f.t, result)
 
+	return customResult
+}
+
+// standardTestRunner is the implementation of the default test runner
+type standardTestRunner struct{}
+
+func (s *standardTestRunner) FinalPreparer(result *TestResult) CustomTestResult {
+	// Register the hard coded mutators and singletons used by the standard Soong build as well as
+	// any additional instances that have been registered with this fixture.
+	result.TestContext.Register()
 	return result
 }
 
+func (s *standardTestRunner) PostParseProcessor(customResult CustomTestResult) {
+	result := customResult.(*TestResult)
+	ctx := result.TestContext
+	cfg := result.Config
+	// Prepare the build actions, i.e. run all the mutators, singletons and then invoke the
+	// GenerateAndroidBuildActions methods on all the modules.
+	extraNinjaDeps, errs := ctx.PrepareBuildActions(cfg)
+	result.NinjaDeps = append(result.NinjaDeps, extraNinjaDeps...)
+	result.CollateErrs(errs)
+}
+
+var defaultTestRunner FixtureTestRunner = &standardTestRunner{}
+
 func (f *fixture) outputDebugState() {
 	fmt.Printf("Begin Fixture State for %s\n", f.t.Name())
 	if len(f.config.env) == 0 {
@@ -909,3 +1034,10 @@
 func (r *TestResult) Module(name string, variant string) Module {
 	return r.ModuleForTests(name, variant).Module()
 }
+
+// CollateErrs adds additional errors to the result and returns true if there is more than one
+// error in the result.
+func (r *TestResult) CollateErrs(errs []error) bool {
+	r.Errs = append(r.Errs, errs...)
+	return len(r.Errs) > 0
+}