Index: tests/phpunit/tests/functions/isPhpVersionCompatible.php
===================================================================
--- tests/phpunit/tests/functions/isPhpVersionCompatible.php	(revision 53229)
+++ tests/phpunit/tests/functions/isPhpVersionCompatible.php	(working copy)
@@ -1,53 +1,89 @@
 <?php
 
 /**
- * Tests the is_php_version_compatible function.
+ * Tests the is_php_version_compatible() function.
  *
  * @group functions.php
  * @covers ::is_php_version_compatible
  */
-class Tests_Functions_isPhpVersionCompatible extends WP_UnitTestCase {
+class Tests_Functions_IsPhpVersionCompatible extends WP_UnitTestCase {
 	/**
 	 * Tests is_php_version_compatible().
 	 *
 	 * @dataProvider data_is_php_version_compatible
 	 *
-	 * @param mixed $test_value
-	 * @param bool $expected
+	 * @ticket 54257
 	 *
-	 * @ticket 54257
+	 * @param mixed $required The minimum required PHP version.
+	 * @param bool  $expected The expected result.
 	 */
-	public function test_is_php_version_compatible( $test_value, $expected ) {
-		$this->assertSame( is_php_version_compatible( $test_value ), $expected );
+	public function test_is_php_version_compatible( $required, $expected ) {
+		$this->assertSame( $expected, is_php_version_compatible( $required ) );
 	}
 
 	/**
-	 * Provides test scenarios for test_php_version_compatible.
+	 * Data provider.
 	 *
 	 * @return array
 	 */
-	function data_is_php_version_compatible() {
+	public function data_is_php_version_compatible() {
 		$php_version = phpversion();
 
-		$more = explode( '.', $php_version );
-		$less = $more;
+		$version_parts  = explode( '.', $php_version );
+		$lower_version  = $version_parts;
+		$higher_version = $version_parts;
 
-		-- $less[ count( $less ) - 1 ];
-		++ $more[ count( $less ) - 1 ];
+		// Adjust the major version numbers.
+		--$lower_version[0];
+		++$higher_version[0];
 
+		$lower_version  = implode( '.', $lower_version );
+		$higher_version = implode( '.', $higher_version );
+
 		return array(
-			'greater' => array(
-				'test_value' => implode( '.', $more ),
-				'expected'   => false,
+			// Happy paths.
+			'a lower required version'  => array(
+				'required' => $lower_version,
+				'expected' => true,
 			),
-			'same'    => array(
-				'test_value' => $php_version,
-				'expected'   => true,
+			'the same version'          => array(
+				'required' => $php_version,
+				'expected' => true,
 			),
-			'less'    => array(
-				'test_value' => implode( '.', $less ),
-				'expected'   => true,
+			'a higher required version' => array(
+				'required' => $higher_version,
+				'expected' => false,
 			),
+
+			// Falsey values.
+			'false'                     => array(
+				'required' => false,
+				'expected' => true,
+			),
+			'null'                      => array(
+				'required' => null,
+				'expected' => true,
+			),
+			'0 int'                     => array(
+				'required' => 0,
+				'expected' => true,
+			),
+			'0.0 float'                 => array(
+				'required' => 0.0,
+				'expected' => true,
+			),
+			'0 string'                  => array(
+				'required' => '0',
+				'expected' => true,
+			),
+			'empty string'              => array(
+				'required' => '',
+				'expected' => true,
+			),
+			'empty array'               => array(
+				'required' => array(),
+				'expected' => true,
+			),
 		);
 	}
 }
Index: tests/phpunit/tests/functions/isWpVersionCompatible.php
===================================================================
--- tests/phpunit/tests/functions/isWpVersionCompatible.php	(revision 53229)
+++ tests/phpunit/tests/functions/isWpVersionCompatible.php	(working copy)
@@ -1,53 +1,184 @@
 <?php
 
 /**
- * Tests the is_php_version_compatible function.
+ * Tests the is_wp_version_compatible() function.
  *
  * @group functions.php
  * @covers ::is_wp_version_compatible
  */
-class Tests_Functions_isWpVersionCompatible extends WP_UnitTestCase {
+class Tests_Functions_IsWpVersionCompatible extends WP_UnitTestCase {
 	/**
-	 * Test is_wp_version_compatible().
+	 * Tests is_wp_version_compatible().
 	 *
 	 * @dataProvider data_is_wp_version_compatible
 	 *
-	 * @param mixed $test_value
-	 * @param bool $expected
+	 * @ticket 54257
 	 *
+	 * @param mixed $required The minimum required WordPress version.
+	 * @param bool  $expected The expected result.
+	 */
+	public function test_is_wp_version_compatible( $required, $expected ) {
+		$this->assertSame( $expected, is_wp_version_compatible( $required ) );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array
+	 */
+	public function data_is_wp_version_compatible() {
+		global $wp_version;
+
+		$version_parts  = explode( '.', $wp_version );
+		$lower_version  = $version_parts;
+		$higher_version = $version_parts;
+
+		// Adjust the major version numbers.
+		--$lower_version[0];
+		++$higher_version[0];
+
+		$lower_version  = implode( '.', $lower_version );
+		$higher_version = implode( '.', $higher_version );
+
+		return array(
+			// Happy paths.
+			'the same version'          => array(
+				'required' => $wp_version,
+				'expected' => true,
+			),
+			'a lower required version'  => array(
+				'required' => $lower_version,
+				'expected' => true,
+			),
+			'a higher required version' => array(
+				'required' => $higher_version,
+				'expected' => false,
+			),
+
+			// Falsey values.
+			'false'                     => array(
+				'required' => false,
+				'expected' => true,
+			),
+			'null'                      => array(
+				'required' => null,
+				'expected' => true,
+			),
+			'0 int'                     => array(
+				'required' => 0,
+				'expected' => true,
+			),
+			'0.0 float'                 => array(
+				'required' => 0.0,
+				'expected' => true,
+			),
+			'0 string'                  => array(
+				'required' => '0',
+				'expected' => true,
+			),
+			'empty string'              => array(
+				'required' => '',
+				'expected' => true,
+			),
+			'empty array'               => array(
+				'required' => array(),
+				'expected' => true,
+			),
+		);
+	}
+
+	/**
+	 * Tests is_wp_version_compatible() with development versions.
+	 *
+	 * @dataProvider data_is_wp_version_compatible_with_development_versions
+	 *
 	 * @ticket 54257
+	 *
+	 * @param string $required  The minimum required WordPress version.
+	 * @param string $wp        The value for the $wp_version global variable.
+	 * @param bool   $expected  The expected result.
 	 */
-	public function test_is_wp_version_compatible( $test_value, $expected ) {
-		$this->assertSame( is_wp_version_compatible( $test_value ), $expected );
+	public function test_is_wp_version_compatible_with_development_versions( $required, $wp, $expected ) {
+		global $wp_version;
+
+		$original_version = $wp_version;
+		$wp_version       = $wp;
+		$actual           = is_wp_version_compatible( $required );
+
+		// Reset the version before the assertion in case of failure.
+		$wp_version = $original_version;
+
+		$this->assertSame( $expected, $actual );
 	}
 
 	/**
-	 * Provides test scenarios test_is_wp_version_compatible.
+	 * Data provider.
 	 *
 	 * @return array
 	 */
-	function data_is_wp_version_compatible() {
-		$wp_version = get_bloginfo( 'version' );
+	public function data_is_wp_version_compatible_with_development_versions() {
+		global $wp_version;
 
-		$more = explode( '.', $wp_version );
-		$less = $more;
+		// For consistent results, remove possible suffixes.
+		list( $version ) = explode( '-', $wp_version );
 
-		-- $less[0];
-		++ $more[0];
+		$version_parts  = explode( '.', $version );
+		$lower_version  = $version_parts;
+		$higher_version = $version_parts;
 
+		// Adjust the major version numbers.
+		--$lower_version[0];
+		++$higher_version[0];
+
+		$lower_version  = implode( '.', $lower_version );
+		$higher_version = implode( '.', $higher_version );
+
 		return array(
-			'greater' => array(
-				'test_value' => implode( '.', $more ),
-				'expected'   => false,
+			'a lower required version and an alpha wordpress version' => array(
+				'required' => $lower_version,
+				'wp'       => $version . '-alpha-12341-src',
+				'expected' => true,
 			),
-			'same'    => array(
-				'test_value' => $wp_version,
-				'expected'   => true,
+			'a lower required version and a beta wordpress version'   => array(
+				'required' => $lower_version,
+				'wp'       => $version . '-beta1',
+				'expected' => true,
 			),
-			'less'    => array(
-				'test_value' => implode( '.', $less ),
-				'expected'   => true,
+			'a lower required version and a release candidate wordpress version'   => array(
+				'required' => $lower_version,
+				'wp'       => $version . '-RC1',
+				'expected' => true,
 			),
+			'the same required version and an alpha wordpress version' => array(
+				'required' => $version,
+				'wp'       => $version . '-alpha-12341-src',
+				'expected' => true,
+			),
+			'the same required version and a beta wordpress version' => array(
+				'required' => $version,
+				'wp'       => $version . '-beta1',
+				'expected' => true,
+			),
+			'the same required version and a release candidate wordpress version' => array(
+				'required' => $version,
+				'wp'       => $version . '-RC1',
+				'expected' => true,
+			),
+			'a higher required version and an alpha wordpress version'   => array(
+				'required' => $higher_version,
+				'wp'       => $version . '-alpha-12341-src',
+				'expected' => false,
+			),
+			'a higher required version and a beta wordpress version'   => array(
+				'required' => $higher_version,
+				'wp'       => $version . '-beta1',
+				'expected' => false,
+			),
+			'a higher required version and a release candidate wordpress version'   => array(
+				'required' => $higher_version,
+				'wp'       => $version . '-RC1',
+				'expected' => false,
+			),
 		);
 	}
 }