Verify the prebuilt_apex selects the correct input apex file

This will ensure that the following refactoring does not change the
behavior.

Bug: 181267622
Test: m nothing
Change-Id: Ieb9b37c2a1ef609b2d6565c54c261439a1ce7147
diff --git a/apex/apex_test.go b/apex/apex_test.go
index 443fba3..41f43fe 100644
--- a/apex/apex_test.go
+++ b/apex/apex_test.go
@@ -4419,6 +4419,13 @@
 			t.Errorf("expected: %q, found: %q", expected, actual)
 		}
 
+		// Make sure that the prebuilt_apex has the correct input APEX.
+		prebuiltApex := ctx.ModuleForTests("myapex", "android_common")
+		rule = prebuiltApex.Rule("android/soong/android.Cp")
+		if expected, actual := "myapex-arm64.apex", android.NormalizePathForTesting(rule.Input); !reflect.DeepEqual(expected, actual) {
+			t.Errorf("expected: %q, found: %q", expected, actual)
+		}
+
 		checkDexJarBuildPath(t, ctx, "libfoo")
 
 		checkDexJarBuildPath(t, ctx, "libbar")