Add SetupAndroidProject.kt

A rule in case you have not exported the ANDROID_SDK_ROOT environment
property.

Author: mezpahlan

affectedmoduledetector/src/test/kotlin/com/dropbox/affectedmoduledetector/AffectedModuleDetectorIntegrationTest.kt

@@ -1,38 +1,38 @@
 package com.dropbox.affectedmoduledetector
 
+import com.dropbox.affectedmoduledetector.rules.SetupAndroidProject
 import com.google.common.truth.Truth.assertThat
 import org.gradle.testkit.runner.GradleRunner
 import org.junit.Rule
 import org.junit.Test
-import org.junit.rules.TemporaryFolder
 
 class AffectedModuleDetectorIntegrationTest {
 
     @Rule
     @JvmField
-    val tmpFolder = TemporaryFolder()
+    val tmpFolder = SetupAndroidProject()
 
     @Test
     fun `GIVEN single project WHEN plugin is applied THEN tasks are added`() {
         // GIVEN
         // expected tasks
         val tasks = listOf(
-                "runAffectedUnitTests",
-                "runAffectedAndroidTests",
-                "assembleAffectedAndroidTests"
+            "runAffectedUnitTests",
+            "runAffectedAndroidTests",
+            "assembleAffectedAndroidTests"
         )
         tmpFolder.newFile("build.gradle").writeText(
-                """plugins {
+            """plugins {
                 |   id "com.dropbox.affectedmoduledetector"
                 |}""".trimMargin()
         )
 
         // WHEN
         val result = GradleRunner.create()
-                .withProjectDir(tmpFolder.root)
-                .withPluginClasspath()
-                .withArguments("tasks")
-                .build()
+            .withProjectDir(tmpFolder.root)
+            .withPluginClasspath()
+            .withArguments("tasks")
+            .build()
 
         // THEN
         tasks.forEach { taskName ->
@@ -43,17 +43,18 @@ class AffectedModuleDetectorIntegrationTest {
     @Test
     fun `GIVEN multiple project WHEN plugin is applied THEN tasks has dependencies`() {
         // GIVEN
+        tmpFolder.setupAndroidSdkLocation()
         tmpFolder.newFolder("sample-app")
         tmpFolder.newFolder("sample-core")
         tmpFolder.newFile("settings.gradle").writeText(
-                """
+            """
                 |include ':sample-app'
                 |include ':sample-core'
                 """.trimMargin()
         )
 
         tmpFolder.newFile("build.gradle").writeText(
-                """buildscript {
+            """buildscript {
                 |   repositories {
                 |       google()
                 |       jcenter()
@@ -75,7 +76,7 @@ class AffectedModuleDetectorIntegrationTest {
         )
 
         tmpFolder.newFile("sample-app/build.gradle").writeText(
-                """plugins {
+            """plugins {
                 |     id 'com.android.application'
                 |     id 'kotlin-android'
                 |   }
@@ -89,7 +90,7 @@ class AffectedModuleDetectorIntegrationTest {
         )
 
         tmpFolder.newFile("sample-core/build.gradle").writeText(
-                """plugins {
+            """plugins {
                 |   id 'com.android.library'
                 |   id 'kotlin-android'
                 |   }
@@ -104,10 +105,10 @@ class AffectedModuleDetectorIntegrationTest {
 
         // WHEN
         val result = GradleRunner.create()
-                .withProjectDir(tmpFolder.root)
-                .withPluginClasspath()
-                .withArguments("assembleAffectedAndroidTests", "--dry-run")
-                .build()
+            .withProjectDir(tmpFolder.root)
+            .withPluginClasspath()
+            .withArguments("assembleAffectedAndroidTests", "--dry-run")
+            .build()
 
         // THEN
         assertThat(result.output).contains(":sample-app:assembleDebugAndroidTest SKIPPED")

affectedmoduledetector/src/test/kotlin/com/dropbox/affectedmoduledetector/rules/SetupAndroidProject.kt

@@ -0,0 +1,44 @@
+package com.dropbox.affectedmoduledetector.rules
+
+import org.junit.rules.TemporaryFolder
+import java.io.File
+import java.io.FileNotFoundException
+
+/**
+ * TestRule that allows setup of the Android SDK within the context of a GradleRunner test.
+ */
+class SetupAndroidProject : TemporaryFolder() {
+
+    /**
+     * Setup the Android SDK location for test involving Gradle and the Android Gradle DSL.
+     *
+     * Users may have configured their machine with an environment variable ANDROID_SDK_ROOT in
+     * which case the Android SDK will automatically be found using this. Otherwise we attempt to
+     * local the machine specific local.properties file and copy the contents.
+     */
+    fun setupAndroidSdkLocation() {
+        // If we happen to have already set this environment variable then we are all good to go.
+        // Nothing to see here. Move along.
+        if (!System.getenv("ANDROID_SDK_ROOT").isNullOrBlank()) return
+
+        // Find the local.properties file. File works relative to the nearest build.gradle which
+        // is the one for the Gradle module that we are currently running tests in - not the root
+        // project. But assuming that we will only ever be one level deep then we can simply use
+        // ".." to go up one level where we _should_ find our file.
+        val localDotProperties = File("../local.properties")
+
+        if (!localDotProperties.exists()) throw FileNotFoundException(
+            """
+                |Unable to locate Android SDK. Ensure that you have either the ANDROID_SDK_ROOT 
+                |environment variable set or the sdk.dir location correctly set in local
+                |.properties within the Gradle root project directory.
+            """.trimMargin()
+        )
+
+        // Read our machine specific local.properties file and copy it to our temp Gradle test
+        // directory for the test.
+        localDotProperties.bufferedReader().use {
+            newFile("local.properties").writeText(it.readText())
+        }
+    }
+}