Tests: Improve coverage for url_shorten() and test the $length parameter.

The case meant to test the optional `$length` parameter passed it as an argument to `assertSame()` instead of `url_shorten()`. So the latter ran with its default length of 35, the expected value happened to match the default output, and the assertion passed — while the `$length` parameter was never actually tested.

This commit:

* Converts the tests to a data provider with descriptive keys, so a failure points to the exact case.
* Separates the default-behavior cases from the custom-length cases.
* Adds real coverage for `$length`: the URL is kept when the length exceeds or equals the cleaned URL (pinning the strict `>` comparison) and shortened when it is smaller.
* Adds a comment clarifying that a shortened URL is cut to `( $length - 3 )` characters before `…` is appended.

No production code is changed — this is a test-only improvement.

Developed in WordPress#12558.

Follow-up to [35314].

Props Soean, mukesh27, SergeyBiryukov.
See #64894.

git-svn-id: https://develop.svn.wordpress.org/trunk@62768 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

tests/phpunit/tests/formatting/urlShorten.php

@@ -6,20 +6,80 @@
  * @covers ::url_shorten
  */
 class Tests_Formatting_UrlShorten extends WP_UnitTestCase {
-	public function test_url_shorten() {
-		$tests = array(
-			'wordpress\.org/about/philosophy'            => 'wordpress\.org/about/philosophy', // No longer strips slashes.
-			'wordpress.org/about/philosophy'             => 'wordpress.org/about/philosophy',
-			'http://wordpress.org/about/philosophy/'     => 'wordpress.org/about/philosophy',  // Remove http, trailing slash.
-			'http://www.wordpress.org/about/philosophy/' => 'wordpress.org/about/philosophy',  // Remove http, www.
-			'http://wordpress.org/about/philosophy/#box' => 'wordpress.org/about/philosophy/#box',            // Don't shorten 35 characters.
-			'http://wordpress.org/about/philosophy/#decisions' => 'wordpress.org/about/philosophy/#…', // Shorten to 32 if > 35 after cleaning.
+
+	/**
+	 * @dataProvider data_url_shorten
+	 *
+	 * @param string $url      URL to shorten.
+	 * @param string $expected Expected shortened URL.
+	 */
+	public function test_url_shorten( $url, $expected ) {
+		$this->assertSame( $expected, url_shorten( $url ) );
+	}
+
+	public function data_url_shorten() {
+		// When shortened, the URL is cut to ( $length - 3 ) characters before '…' is appended.
+		return array(
+			'escaped slashes are not stripped' => array(
+				'wordpress\.org/about/philosophy',
+				'wordpress\.org/about/philosophy',
+			),
+			'no change needed'                 => array(
+				'wordpress.org/about/philosophy',
+				'wordpress.org/about/philosophy',
+			),
+			'http and trailing slash removed'  => array(
+				'http://wordpress.org/about/philosophy/',
+				'wordpress.org/about/philosophy',
+			),
+			'http and www removed'             => array(
+				'http://www.wordpress.org/about/philosophy/',
+				'wordpress.org/about/philosophy',
+			),
+			'exactly 35 characters kept'       => array(
+				'http://wordpress.org/about/philosophy/#box',
+				'wordpress.org/about/philosophy/#box',
+			),
+			'shortened to 32 when over 35'     => array(
+				'http://wordpress.org/about/philosophy/#decisions',
+				'wordpress.org/about/philosophy/#…',
+			),
 		);
-		foreach ( $tests as $k => $v ) {
-			$this->assertSame( $v, url_shorten( $k ) );
-		}
+	}
 
-		// Shorten to 31 if > 34 after cleaning.
-		$this->assertSame( 'wordpress.org/about/philosophy/#…', url_shorten( 'http://wordpress.org/about/philosophy/#decisions' ), 31 );
+	/**
+	 * Ensures the optional $length parameter overrides the default of 35.
+	 *
+	 * @dataProvider data_url_shorten_custom_length
+	 *
+	 * @param string $url      URL to shorten.
+	 * @param int    $length   Maximum length of the shortened URL.
+	 * @param string $expected Expected shortened URL.
+	 */
+	public function test_url_shorten_respects_custom_length( $url, $length, $expected ) {
+		$this->assertSame( $expected, url_shorten( $url, $length ) );
+	}
+
+	public function data_url_shorten_custom_length() {
+		// The URL below is 41 characters long after cleaning.
+		$url = 'http://wordpress.org/about/philosophy/#decisions';
+
+		return array(
+			'kept when length exceeds the URL' => array(
+				$url,
+				100,
+				'wordpress.org/about/philosophy/#decisions',
+			),
+			'kept when length equals the URL'  => array(
+				$url,
+				41,
+				'wordpress.org/about/philosophy/#decisions',
+			),
+			'shortened when length is smaller' => array(
+				$url,
+				40,
+				'wordpress.org/about/philosophy/#decis…',
+			),
+		);
 	}
 }