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GoogleTest

src/android/testing/googletest.md

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<!-- Copyright 2024 Google LLC SPDX-License-Identifier: CC-BY-4.0 -->

GoogleTest

The GoogleTest crate allows for flexible test assertions using matchers:

rust,ignore
# // Copyright 2024 Google LLC
# // SPDX-License-Identifier: Apache-2.0
#
{{#include googletest.rs:test_elements_are}}

If we change the last element to "!", the test fails with a structured error message pin-pointing the error:

<!-- mdbook-xgettext: skip -->
text
---- 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
<details>

  • GoogleTest is not part of the Rust Playground, so you need to run this example in a local environment. Use cargo add googletest to quickly add it to an existing Cargo project.

  • The use googletest::prelude::*; line imports a number of commonly used macros and types.

  • 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:

rust,ignore
# // Copyright 2024 Google LLC
# // SPDX-License-Identifier: Apache-2.0
#
{{#include googletest.rs:test_multiline_string_diff}}

shows a color-coded diff (colors not shown here):

<!-- mdbook-xgettext: skip -->
text
    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
</details>