Corona: Add delete from cache function

Reviewed at https://reviews.lunr.nl/r/1035/

src/Lunr/Corona/Model.php

@@ -109,6 +109,18 @@ protected function cache_if_needed(string $id, callable $callable, array $args =
         return $value;
     }
 
+    /**
+     * Delete cache item.
+     *
+     * @param string $key Unique identifier for the data.
+     *
+     * @return bool True if the item was successfully removed. False if there was an error.
+     */
+    protected function delete_from_cache(string $key): bool
+    {
+        return $this->cache->deleteItem($key);
+    }
+
 }
 
 ?>

src/Lunr/Corona/Tests/ModelCacheTest.php

@@ -249,6 +249,23 @@ public function testCacheIfNeededCachesWhenNeededWithArgs()
         $this->assertEquals('test param', $result);
     }
 
+    /**
+     * Test that delete_from_cache() deletes value from cache.
+     *
+     * @covers \Lunr\Corona\Model::delete_from_cache
+     */
+    public function testDeleteFromCache()
+    {
+        $this->cache->expects($this->once())
+                    ->method('deleteItem')
+                    ->with('foo')
+                    ->willReturn(TRUE);
+
+        $method = $this->get_accessible_reflection_method('delete_from_cache');
+
+        $method->invokeArgs($this->class, [ 'foo' ]);
+    }
+
 }
 
 ?>