diff --git a/android/bazel_test.go b/android/bazel_test.go
new file mode 100644
index 0000000..e5d8fbb
--- /dev/null
+++ b/android/bazel_test.go
@@ -0,0 +1,134 @@
+// Copyright 2021 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package android
+
+import "testing"
+
+func TestConvertAllModulesInPackage(t *testing.T) {
+	testCases := []struct {
+		prefixes   Bp2BuildConfig
+		packageDir string
+	}{
+		{
+			prefixes: Bp2BuildConfig{
+				"a": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "a",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a/b": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "a/b",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a/b":   Bp2BuildDefaultTrueRecursively,
+				"a/b/c": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "a/b",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a":     Bp2BuildDefaultTrueRecursively,
+				"d/e/f": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "a/b",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a":     Bp2BuildDefaultFalse,
+				"a/b":   Bp2BuildDefaultTrueRecursively,
+				"a/b/c": Bp2BuildDefaultFalse,
+			},
+			packageDir: "a/b",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a":     Bp2BuildDefaultTrueRecursively,
+				"a/b":   Bp2BuildDefaultFalse,
+				"a/b/c": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "a",
+		},
+	}
+
+	for _, test := range testCases {
+		if !bp2buildDefaultTrueRecursively(test.packageDir, test.prefixes) {
+			t.Errorf("Expected to convert all modules in %s based on %v, but failed.", test.packageDir, test.prefixes)
+		}
+	}
+}
+
+func TestModuleOptIn(t *testing.T) {
+	testCases := []struct {
+		prefixes   Bp2BuildConfig
+		packageDir string
+	}{
+		{
+			prefixes: Bp2BuildConfig{
+				"a/b": Bp2BuildDefaultFalse,
+			},
+			packageDir: "a/b",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a":   Bp2BuildDefaultFalse,
+				"a/b": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "a",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a/b": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "a", // opt-in by default
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a/b/c": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "a/b",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a":     Bp2BuildDefaultTrueRecursively,
+				"d/e/f": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "foo/bar",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a":     Bp2BuildDefaultTrueRecursively,
+				"a/b":   Bp2BuildDefaultFalse,
+				"a/b/c": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "a/b",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a":     Bp2BuildDefaultFalse,
+				"a/b":   Bp2BuildDefaultTrueRecursively,
+				"a/b/c": Bp2BuildDefaultFalse,
+			},
+			packageDir: "a",
+		},
+	}
+
+	for _, test := range testCases {
+		if bp2buildDefaultTrueRecursively(test.packageDir, test.prefixes) {
+			t.Errorf("Expected to allow module opt-in in %s based on %v, but failed.", test.packageDir, test.prefixes)
+		}
+	}
+}