Add unit tests for Smilies::isEmojiPost

- Current implementation is failing tests with emojis including the zero-width-joiner character, encoded on 3 bytes only.

src/Content/Smilies.php

@@ -289,11 +289,12 @@ class Smilies
 	/**
 	 * Checks if the body only contains 4 byte unicode characters.
 	 *
-	 * @param string $body
+	 * @param string $body Possibly-HTML post body
 	 * @return boolean
 	 */
 	public static function isEmojiPost(string $body): bool
 	{
+		// Strips all whitespace
 		$conv = preg_replace('#\s#u', '', html_entity_decode($body));
 		// Emojis are always 4 byte Unicode characters
 		return (!empty($conv) && (strlen($conv) / mb_strlen($conv) == 4));

tests/src/Content/SmiliesTest.php

@@ -72,4 +72,75 @@ class SmiliesTest extends FixtureTest
 		$output = Smilies::replaceFromArray($text, $smilies);
 		self::assertEquals($expected, $output);
 	}
+
+	public function dataIsEmojiPost(): array
+	{
+		return [
+			'emoji' => [
+				'expected' => true,
+				'body' => '👀',
+			],
+			'emojis' => [
+				'expected' => true,
+				'body' => '👀🤷',
+			],
+			'emoji+whitespace' => [
+				'expected' => true,
+				'body' => ' 👀 ',
+			],
+			'empty' => [
+				'expected' => false,
+				'body' => '',
+			],
+			'whitespace' => [
+				'expected' => false,
+				'body' => '
+				',
+			],
+			'emoji+ASCII' => [
+				'expected' => false,
+				'body' => '🤷a',
+			],
+			'HTML entity whitespace' => [
+				'expected' => false,
+				'body' => ' ',
+			],
+			'HTML entity else' => [
+				'expected' => false,
+				'body' => '°',
+			],
+			'emojis+HTML whitespace' => [
+				'expected' => true,
+				'body' => '👀 🤷',
+			],
+			'emojis+HTML else' => [
+				'expected' => false,
+				'body' => '👀<🤷',
+			],
+			'zwj' => [
+				'expected' => true,
+				'body' => '👨‍👨‍👧‍',
+			],
+			'zwj+whitespace' => [
+				'expected' => true,
+				'body' => ' 👨‍👨‍👧‍ ',
+			],
+			'zwj+HTML whitespace' => [
+				'expected' => true,
+				'body' => ' 👨‍👨‍👧‍ ',
+			],
+		];
+	}
+
+	/**
+	 * @dataProvider dataIsEmojiPost
+	 *
+	 * @param bool   $expected
+	 * @param string $body
+	 * @return void
+	 */
+	public function testIsEmojiPost(bool $expected, string $body)
+	{
+		$this->assertEquals($expected, Smilies::isEmojiPost($body));
+	}
 }