Add preparer for test to allow missing dependencies

Bug: 181070625
Test: m nothing
Change-Id: I426fcb19d9bea8b9551dc5c3a803228a34768fc0
diff --git a/android/testing.go b/android/testing.go
index 03d7bd5..dd3d607 100644
--- a/android/testing.go
+++ b/android/testing.go
@@ -24,6 +24,7 @@
 	"testing"
 
 	"github.com/google/blueprint"
+	"github.com/google/blueprint/proptools"
 )
 
 func NewTestContext(config Config) *TestContext {
@@ -105,6 +106,17 @@
 	PrepareForTestWithAndroidBuildComponents,
 )
 
+// Prepares a test that may be missing dependencies by setting allow_missing_dependencies to
+// true.
+var PrepareForTestWithAllowMissingDependencies = GroupFixturePreparers(
+	FixtureModifyProductVariables(func(variables FixtureProductVariables) {
+		variables.Allow_missing_dependencies = proptools.BoolPtr(true)
+	}),
+	FixtureModifyContext(func(ctx *TestContext) {
+		ctx.SetAllowMissingDependencies(true)
+	}),
+)
+
 func NewTestArchContext(config Config) *TestContext {
 	ctx := NewTestContext(config)
 	ctx.preDeps = append(ctx.preDeps, registerArchMutator)