Add tests for index reflection

Fix issues with primary key reflection and add missing tests for
reflection of KEY statements.

lib/Cake/Database/Schema/MysqlSchema.php

@@ -183,7 +183,7 @@ public function convertIndexDescription(Table $table, $row) {
 			$type = strtolower($row['Index_type']);
 		} elseif ($row['Non_unique'] == 0 && $type !== 'primary') {
 			$type = 'unique';
-		} else {
+		} elseif ($type !== 'primary') {
 			$type = 'index';
 		}
 
@@ -203,7 +203,7 @@ public function convertIndexDescription(Table $table, $row) {
 		// MySQL multi column indexes come back
 		// as multiple rows.
 		if (!empty($existing)) {
-			$columns = array_merge($existing['columns'], $columns);
+			$columns = array_unique(array_merge($existing['columns'], $columns));
 			$length = array_merge($existing['length'], $length);
 		}
 		if ($isIndex) {

lib/Cake/Test/TestCase/Database/Schema/MysqlSchemaTest.php

@@ -282,6 +282,8 @@ public function testDescribeTableIndexes() {
 		$schema = new SchemaCollection($connection);
 		$result = $schema->describe('articles');
 		$this->assertInstanceOf('Cake\Database\Schema\Table', $result);
+
+		$this->assertCount(2, $result->constraints());
 		$expected = [
 			'primary' => [
 				'type' => 'primary',
@@ -296,13 +298,16 @@ public function testDescribeTableIndexes() {
 				]
 			]
 		];
-		foreach ($expected as $name => $props) {
-			$this->assertEquals(
-				$props,
-				$result->constraint($name),
-				'Index definition does not match for ' . $name
-			);
-		}
+		$this->assertEquals($expected['primary'], $result->constraint('primary'));
+		$this->assertEquals($expected['length_idx'], $result->constraint('length_idx'));
+
+		$this->assertCount(1, $result->indexes());
+		$expected = [
+			'type' => 'index',
+			'columns' => ['author_id'],
+			'length' => []
+		];
+		$this->assertEquals($expected, $result->index('author_idx'));
 	}
 
 /**