Add test to verify the deapexer rule's input apex file

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

Bug: 181267622
Test: m nothing
Change-Id: I36ae9ec9a0a7977bd394f4100c72941052d763ac
diff --git a/apex/apex_test.go b/apex/apex_test.go
index 82fc955..443fba3 100644
--- a/apex/apex_test.go
+++ b/apex/apex_test.go
@@ -4412,6 +4412,13 @@
 		// Make sure that dexpreopt can access dex implementation files from the prebuilt.
 		ctx := testDexpreoptWithApexes(t, bp, "", transform)
 
+		// Make sure that the deapexer has the correct input APEX.
+		deapexer := ctx.ModuleForTests("myapex.deapexer", "android_common")
+		rule := deapexer.Rule("deapexer")
+		if expected, actual := []string{"myapex-arm64.apex"}, android.NormalizePathsForTesting(rule.Implicits); !reflect.DeepEqual(expected, actual) {
+			t.Errorf("expected: %q, found: %q", expected, actual)
+		}
+
 		checkDexJarBuildPath(t, ctx, "libfoo")
 
 		checkDexJarBuildPath(t, ctx, "libbar")