GoogleTest

GoogleTest クレートにより、マッチャーを使用した柔軟なテスト アサーションが可能になります。

use googletest::prelude::*; #[googletest::test] fn test_elements_are() { let value = vec!["foo", "bar", "baz"]; expect_that!(value, elements_are!(eq(&"foo"), lt(&"xyz"), starts_with("b"))); }

最後の要素を "!" に変更すると、テストは失敗し、エラー箇所を示す構造化されたエラー メッセージが表示されます。

---- test_elements_are stdout ---- Value of: value Expected: has elements: 0. is equal to "foo" 1. is less than "xyz" 2. starts with prefix "!" Actual: ["foo", "bar", "baz"], where element #2 is "baz", which does not start with "!" at src/testing/googletest.rs:6:5 Error: See failure output above

Speaker Notes

This slide should take about 5 minutes.
  • GoogleTest は Rust プレイグラウンドの一部ではないため、この例はローカル環境で実行する必要があります。cargo add googletest を使用して、既存の Cargo プロジェクトにすばやく追加します。

  • use googletest::prelude::*; 行は、一般的に使用されるマクロと型をインポートします。

  • This just scratches the surface, there are many builtin matchers. Consider going through the first chapter of “Advanced testing for Rust applications”, a self-guided Rust course: it provides a guided introduction to the library, with exercises to help you get comfortable with googletest macros, its matchers and its overall philosophy.

  • A particularly nice feature is that mismatches in multi-line strings are shown as a diff:

#[test] fn test_multiline_string_diff() { let haiku = "Memory safety found,\n\ Rust's strong typing guides the way,\n\ Secure code you'll write."; assert_that!( haiku, eq("Memory safety found,\n\ Rust's silly humor guides the way,\n\ Secure code you'll write.") ); }

これにより、差分が色分けされます(ここでは色分けされていません)。

Value of: haiku Expected: is equal to "Memory safety found,\nRust's silly humor guides the way,\nSecure code you'll write." Actual: "Memory safety found,\nRust's strong typing guides the way,\nSecure code you'll write.", which isn't equal to "Memory safety found,\nRust's silly humor guides the way,\nSecure code you'll write." Difference(-actual / +expected): Memory safety found, -Rust's strong typing guides the way, +Rust's silly humor guides the way, Secure code you'll write. at src/testing/googletest.rs:17:5