Closes #53: Move test-data config layer into TestCaseTrait

Tests/Fixtures/TestCaseTrait/configTestData.php

@@ -0,0 +1,10 @@
+<?php
+
+return [
+	'test_data' => [
+		[
+			'input'    => 'foo',
+			'expected' => 'bar',
+		],
+	],
+];

Tests/Fixtures/TestCaseTrait/loadTestDataConfig.php

@@ -0,0 +1,10 @@
+<?php
+
+return [
+	'structure' => [
+		'foo' => 'bar',
+	],
+	'test_data' => [
+		'baz' => 'qux',
+	],
+];

Tests/Unit/TestCaseTrait/TestCase.php

@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace WPMedia\PHPUnit\Tests\Unit\TestCaseTrait;
+
+use WPMedia\PHPUnit\Unit\TestCase as BaseTestCase;
+
+abstract class TestCase extends BaseTestCase {
+}
+
+/**
+ * Concrete class declared in this file on purpose: {@see \WPMedia\PHPUnit\TestCaseTrait::loadTestDataConfig()}
+ * resolves the fixture path from the class's own file location, and no `TestCase.php` fixture exists under
+ * `Tests/Fixtures/TestCaseTrait/`. Used by `Test_LoadTestDataConfig` to cover the "no matching fixture" case.
+ */
+class NoFixtureTestCase extends TestCase {
+}

Tests/Unit/TestCaseTrait/configTestData.php

@@ -0,0 +1,45 @@
+<?php
+
+declare(strict_types=1);
+
+namespace WPMedia\PHPUnit\Tests\Unit\TestCaseTrait;
+
+/**
+ * @covers \WPMedia\PHPUnit\TestCaseTrait::configTestData
+ * @group  TestCaseTrait
+ */
+class Test_ConfigTestData extends TestCase {
+
+	public function testShouldReturnTestDataKeyWhenPresentInFixture() {
+		$this->assertSame(
+			[
+				[
+					'input'    => 'foo',
+					'expected' => 'bar',
+				],
+			],
+			$this->configTestData()
+		);
+	}
+
+	public function testShouldReturnWholeConfigWhenTestDataKeyIsAbsent() {
+		$this->config = [
+			'foo' => 'bar',
+		];
+
+		$this->assertSame( [ 'foo' => 'bar' ], $this->configTestData() );
+	}
+
+	public function testShouldNotReloadConfigWhenAlreadyPopulated() {
+		// First call: lazily loads the fixture.
+		$this->configTestData();
+
+		// Overwrite with a sentinel value that has no `test_data` key.
+		$this->config = [
+			'sentinel' => true,
+		];
+
+		// Second call must not reload from the fixture, since $config is no longer empty.
+		$this->assertSame( [ 'sentinel' => true ], $this->configTestData() );
+	}
+}

Tests/Unit/TestCaseTrait/loadTestDataConfig.php

@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+
+namespace WPMedia\PHPUnit\Tests\Unit\TestCaseTrait;
+
+/**
+ * @covers \WPMedia\PHPUnit\TestCaseTrait::loadTestDataConfig
+ * @group  TestCaseTrait
+ */
+class Test_LoadTestDataConfig extends TestCase {
+
+	public function testShouldPopulateConfigFromMatchingFixture() {
+		$this->loadTestDataConfig();
+
+		$this->assertSame(
+			[
+				'structure' => [
+					'foo' => 'bar',
+				],
+				'test_data' => [
+					'baz' => 'qux',
+				],
+			],
+			$this->config
+		);
+	}
+
+	public function testShouldSetEmptyConfigWhenNoMatchingFixtureFileExists() {
+		$target = new NoFixtureTestCase();
+
+		$method = $this->get_reflective_method( 'loadTestDataConfig', NoFixtureTestCase::class );
+		$method->invoke( $target );
+
+		$this->assertSame( [], $this->getNonPublicPropertyValue( 'config', NoFixtureTestCase::class, $target ) );
+	}
+}

src/TestCaseTrait.php

@@ -7,6 +7,7 @@
 use ReflectionClass;
 use ReflectionException;
 use ReflectionMethod;
+use ReflectionObject;
 use ReflectionProperty;
 
 trait TestCaseTrait {
@@ -33,6 +34,38 @@ protected function getTestData( $dir, $filename ) { // phpcs:ignore WordPress.Na
 			: [];
 	}
 
+	/**
+	 * Structure + test data configuration, lazily loaded by {@see configTestData()}.
+	 *
+	 * @var array
+	 */
+	protected $config = [];
+
+	/**
+	 * Test Data Provider that uses the `'test_data'` key of the config file matching the test class,
+	 * lazily loading it on first use.
+	 *
+	 * @return array
+	 */
+	public function configTestData() { // phpcs:ignore WordPress.NamingConventions.ValidFunctionName.MethodNameInvalid -- Public API method; renaming would be a breaking change for consumers.
+		if ( empty( $this->config ) ) {
+			$this->loadTestDataConfig();
+		}
+
+		return $this->config['test_data'] ?? $this->config;
+	}
+
+	/**
+	 * Loads the test data config file matching the current test class name and location.
+	 *
+	 * @return void
+	 */
+	protected function loadTestDataConfig() { // phpcs:ignore WordPress.NamingConventions.ValidFunctionName.MethodNameInvalid -- Public API method; renaming would be a breaking change for consumers.
+		$file = ( new ReflectionObject( $this ) )->getFileName();
+
+		$this->config = $this->getTestData( dirname( $file ), basename( $file, '.php' ) );
+	}
+
 	/**
 	 * Get reflective access to the private/protected method.
 	 *