Index: tests/meta/query.php
===================================================================
--- tests/meta/query.php	(revision 0)
+++ tests/meta/query.php	(revision 0)
@@ -0,0 +1,82 @@
+<?php
+/**
+ * Test WP_Meta_Query, in wp-includes/meta.php
+ *
+ * @group meta
+ */
+class Tests_Meta_Query extends WP_UnitTestCase {
+
+	function test_default_relation() {
+		$query = new WP_Meta_Query( array( array( 'key' => 'abc' ) ) );
+
+		$this->assertEquals( 'AND', $query->relation );
+	}
+
+	function test_set_relation() {
+
+		$query = new WP_Meta_Query( array( array( 'key' => 'abc' ), 'relation' => 'AND' ) );
+
+		$this->assertEquals( 'AND', $query->relation );
+
+		$query = new WP_Meta_Query( array( array( 'key' => 'abc' ), 'relation' => 'OR' ) );
+
+		$this->assertEquals( 'OR', $query->relation );
+	}
+
+	/**
+	 * Test all key only meta queries use the same INNER JOIN when using relation=OR
+	 * 
+	 * @ticket http://core.trac.wordpress.org/ticket/19729
+	 */
+	function test_single_inner_join_for_keys_only() {
+
+		global $wpdb;
+
+		$query = new WP_Meta_Query( array( 
+			array( 'key' => 'abc' ),
+			array( 'key' => 'def' ), 
+			'relation' => 'OR' 
+		) );
+
+		$sql = $query->get_sql( 'post', $wpdb->posts, 'ID' );
+
+		$this->assertEquals( 1, substr_count( $sql['join'], 'INNER JOIN' ) );
+
+		// also check mixing key and key => value 
+		
+		$query = new WP_Meta_Query( array( 
+			array( 'key' => 'abc' ),
+			array( 'key' => 'def' ),
+			array( 'key' => 'ghi', 'value' => 'abc' ), 
+			'relation' => 'OR' 
+		) );
+
+		$sql = $query->get_sql( 'post', $wpdb->posts, 'ID' );
+
+		$this->assertEquals( 2, substr_count( $sql['join'], 'INNER JOIN' ) );
+	}
+
+	/**
+	 * Test the conversion between "WP_Query" style meta args (meta_value=x&meta_key=y)
+	 * to a meta query array
+	 */
+	function test_parse_query_vars() {
+
+		$query = new WP_Meta_Query();
+
+		// just meta_value
+		$query->parse_query_vars( array( 'meta_key' => 'abc' ) );
+
+		$this->assertEquals( array( array( 'key' => 'abc' ) ), $query->queries );
+
+		// meta_key & meta_value
+		$query->parse_query_vars( array( 'meta_key' => 'abc', 'meta_value' => 'def' ) );
+
+		$this->assertEquals( array( array( 'key' => 'abc', 'value' => 'def' ) ), $query->queries );
+
+		// meta_compare
+		$query->parse_query_vars( array( 'meta_key' => 'abc', 'meta_compare' => '=>' ) );
+		
+		$this->assertEquals( array( array( 'key' => 'abc', 'compare' => '=>' ) ), $query->queries );
+	}
+}