Improve code coverage

Author: ipundit

lib/Relation.php

@@ -561,6 +561,8 @@ public function includes(): Relation
      * ])
      * # SELECT * FROM users WHERE name = 'Joe' AND email = 'joe@example.com'
      *
+     * @throws ValidationsArgumentError If you pass in a Relation. Relation::and() supports relations
+     * 
      * @return Relation<TModel>
      */
     public function where(): Relation

test/RelationTest.php

@@ -115,6 +115,12 @@ public function testAnd()
         $this->assertEquals('Bill Clinton', $model->name);
     }
 
+    public function testAndRelationThrowsError()
+    {
+        $this->expectException(ValidationsArgumentError::class);
+        Author::where(Author::where("mixedCaseField = 'Bill'"));
+    }
+
     public function testReverseOrder()
     {
         $relation = Author::where(['mixedCaseField' => 'Bill']);