dict: add delete method

dictionary/dictionary.go

@@ -48,3 +48,7 @@ func (d Dictionary) Update(word, definition string) error {
 	}
 	return nil
 }
+
+func (d Dictionary) Delete(word string) {
+	delete(d, word)
+}

dictionary/dictionary_test.go

@@ -91,3 +91,18 @@ func TestUpdate(t *testing.T) {
 		assertError(t, err, ErrWordDoesNotExist)
 	})
 }
+
+func TestDelete(t *testing.T) {
+	t.Run("delete a word", func(t *testing.T) {
+		word := "test"
+		def := "this is just a test"
+		dict := Dictionary{word: def}
+
+		dict.Delete(word)
+		_, err := dict.Search(word)
+		if err == nil {
+			t.Fatal("expected to get an error")
+		}
+		assertError(t, err, ErrNotFound)
+	})
+}