[9.x]Improve test for LazyCollection (#43474)

Author: moharami

tests/Support/SupportLazyCollectionIsLazyTest.php

@@ -143,6 +143,13 @@ public function testContainsIsLazy()
         });
     }
 
+    public function testDoesntContainIsLazy()
+    {
+        $this->assertEnumerates(5, function ($collection) {
+            $collection->doesntContain(5);
+        });
+    }
+
     public function testContainsStrictIsLazy()
     {
         $this->assertEnumerates(5, function ($collection) {
@@ -682,6 +689,13 @@ public function testMedianEnumeratesOnce()
         });
     }
 
+    public function testAvgEnumeratesOnce()
+    {
+        $this->assertEnumeratesOnce(function ($collection) {
+            $collection->avg();
+        });
+    }
+
     public function testMergeIsLazy()
     {
         $this->assertDoesNotEnumerate(function ($collection) {