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<ul class="chapter"><li><a href="ch01-00-introduction.html"><strong>1.</strong> 介绍</a></li><li><ul class="section"><li><a href="ch01-01-installation.html"><strong>1.1.</strong> 安装</a></li><li><a href="ch01-02-hello-world.html"><strong>1.2.</strong> Hello, World!</a></li></ul></li><li><a href="ch02-00-guessing-game-tutorial.html"><strong>2.</strong> 猜猜看教程</a></li><li><a href="ch03-00-common-programming-concepts.html"><strong>3.</strong> 通用编程概念</a></li><li><ul class="section"><li><a href="ch03-01-variables-and-mutability.html"><strong>3.1.</strong> 变量和可变性</a></li><li><a href="ch03-02-data-types.html"><strong>3.2.</strong> 数据类型</a></li><li><a href="ch03-03-how-functions-work.html"><strong>3.3.</strong> 函数如何工作</a></li><li><a href="ch03-04-comments.html"><strong>3.4.</strong> 注释</a></li><li><a href="ch03-05-control-flow.html"><strong>3.5.</strong> 控制流</a></li></ul></li><li><a href="ch04-00-understanding-ownership.html"><strong>4.</strong> 认识所有权</a></li><li><ul class="section"><li><a href="ch04-01-what-is-ownership.html"><strong>4.1.</strong> 什么是所有权</a></li><li><a href="ch04-02-references-and-borrowing.html"><strong>4.2.</strong> 引用 &amp; 借用</a></li><li><a href="ch04-03-slices.html"><strong>4.3.</strong> Slices</a></li></ul></li><li><a href="ch05-00-structs.html"><strong>5.</strong> 结构体</a></li><li><ul class="section"><li><a href="ch05-01-method-syntax.html"><strong>5.1.</strong> 方法语法</a></li></ul></li><li><a href="ch06-00-enums.html"><strong>6.</strong> 枚举和模式匹配</a></li><li><ul class="section"><li><a href="ch06-01-defining-an-enum.html"><strong>6.1.</strong> 定义枚举</a></li><li><a href="ch06-02-match.html"><strong>6.2.</strong> <code>match</code>控制流运算符</a></li><li><a href="ch06-03-if-let.html"><strong>6.3.</strong> <code>if let</code>简单控制流</a></li></ul></li><li><a href="ch07-00-modules.html"><strong>7.</strong> 模块</a></li><li><ul class="section"><li><a href="ch07-01-mod-and-the-filesystem.html"><strong>7.1.</strong> <code>mod</code>和文件系统</a></li><li><a href="ch07-02-controlling-visibility-with-pub.html"><strong>7.2.</strong> 使用<code>pub</code>控制可见性</a></li><li><a href="ch07-03-importing-names-with-use.html"><strong>7.3.</strong> 使用<code>use</code>导入命名</a></li></ul></li><li><a href="ch08-00-common-collections.html"><strong>8.</strong> 通用集合类型</a></li><li><ul class="section"><li><a href="ch08-01-vectors.html"><strong>8.1.</strong> vector</a></li><li><a href="ch08-02-strings.html"><strong>8.2.</strong> 字符串</a></li><li><a href="ch08-03-hash-maps.html"><strong>8.3.</strong> 哈希 map</a></li></ul></li><li><a href="ch09-00-error-handling.html"><strong>9.</strong> 错误处理</a></li><li><ul class="section"><li><a href="ch09-01-unrecoverable-errors-with-panic.html"><strong>9.1.</strong> <code>panic!</code>与不可恢复的错误</a></li><li><a href="ch09-02-recoverable-errors-with-result.html"><strong>9.2.</strong> <code>Result</code>与可恢复的错误</a></li><li><a href="ch09-03-to-panic-or-not-to-panic.html"><strong>9.3.</strong> <code>panic!</code>还是不<code>panic!</code></a></li></ul></li><li><a href="ch10-00-generics.html"><strong>10.</strong> 泛型、trait 和生命周期</a></li><li><ul class="section"><li><a href="ch10-01-syntax.html"><strong>10.1.</strong> 泛型数据类型</a></li><li><a href="ch10-02-traits.html"><strong>10.2.</strong> trait：定义共享的行为</a></li><li><a href="ch10-03-lifetime-syntax.html"><strong>10.3.</strong> 生命周期与引用有效性</a></li></ul></li><li><a href="ch11-00-testing.html"><strong>11.</strong> 测试</a></li><li><ul class="section"><li><a href="ch11-01-writing-tests.html"><strong>11.1.</strong> 编写测试</a></li><li><a href="ch11-02-running-tests.html" class="active"><strong>11.2.</strong> 运行测试</a></li><li><a href="ch11-03-test-organization.html"><strong>11.3.</strong> 测试的组织结构</a></li></ul></li><li><a href="ch12-00-an-io-project.html"><strong>12.</strong> 一个 I/O 项目</a></li><li><ul class="section"><li><a href="ch12-01-accepting-command-line-arguments.html"><strong>12.1.</strong> 接受命令行参数</a></li><li><a href="ch12-02-reading-a-file.html"><strong>12.2.</strong> 读取文件</a></li><li><a href="ch12-03-improving-error-handling-and-modularity.html"><strong>12.3.</strong> 增强错误处理和模块化</a></li><li><a href="ch12-04-testing-the-librarys-functionality.html"><strong>12.4.</strong> 测试库的功能</a></li><li><a href="ch12-05-working-with-environment-variables.html"><strong>12.5.</strong> 处理环境变量</a></li><li><a href="ch12-06-writing-to-stderr-instead-of-stdout.html"><strong>12.6.</strong> 输出到<code>stderr</code>而不是<code>stdout</code></a></li></ul></li><li><a href="ch13-00-functional-features.html"><strong>13.</strong> Rust 中的函数式语言功能</a></li><li><ul class="section"><li><a href="ch13-01-closures.html"><strong>13.1.</strong> 闭包</a></li><li><a href="ch13-02-iterators.html"><strong>13.2.</strong> 迭代器</a></li><li><a href="ch13-03-improving-our-io-project.html"><strong>13.3.</strong> 改进 I/O 项目</a></li><li><a href="ch13-04-performance.html"><strong>13.4.</strong> 性能</a></li></ul></li><li><a 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运行清理代码</a></li><li><a href="ch15-04-rc.html"><strong>15.4.</strong> <code>Rc&lt;T&gt;</code> 引用计数智能指针</a></li><li><a href="ch15-05-interior-mutability.html"><strong>15.5.</strong> <code>RefCell&lt;T&gt;</code>和内部可变性模式</a></li><li><a href="ch15-06-reference-cycles.html"><strong>15.6.</strong> 引用循环和内存泄漏是安全的</a></li></ul></li><li><a href="ch16-00-concurrency.html"><strong>16.</strong> 无畏并发</a></li><li><ul class="section"><li><a href="ch16-01-threads.html"><strong>16.1.</strong> 线程</a></li><li><a href="ch16-02-message-passing.html"><strong>16.2.</strong> 消息传递</a></li><li><a href="ch16-03-shared-state.html"><strong>16.3.</strong> 共享状态</a></li><li><a href="ch16-04-extensible-concurrency-sync-and-send.html"><strong>16.4.</strong> 可扩展的并发：<code>Sync</code>和<code>Send</code></a></li></ul></li><li><a href="ch17-00-oop.html"><strong>17.</strong> 面向对象</a></li><li><ul class="section"><li><a href="ch17-01-what-is-oo.html"><strong>17.1.</strong> 什么是面向对象</a></li></ul></li></ul>
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<h1 class="menu-title">Rust 程序设计语言 简体中文版</h1>
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<a class="header" href="#运行测试" name="运行测试"><h2>运行测试</h2></a>
<blockquote>
<p><a href="https://github.com/rust-lang/book/blob/master/second-edition/src/ch11-02-running-tests.md">ch11-02-running-tests.md</a>
<br>
commit 55b294f20fc846a13a9be623bf322d8b364cee77</p>
</blockquote>
<p>就像<code>cargo run</code>会编译代码并运行生成的二进制文件，<code>cargo test</code>在测试模式下编译代码并运行生成的测试二进制文件。这里有一些选项可以用来改变<code>cargo test</code>的默认行为。例如，<code>cargo test</code>生成的二进制文件的默认行为是并行的运行所有测试，并捕获测试运行过程中产生的输出避免他们被显示出来使得阅读测试结果相关的内容变得更容易。可以指定命令行参数来改变这些默认行为。</p>
<p>这些选项的一部分可以传递给<code>cargo test</code>，而另一些则需要传递给生成的测试二进制文件。为了分隔两种类型的参数，首先列出传递给<code>cargo test</code>的参数，接着是分隔符<code>--</code>，再之后是传递给测试二进制文件的参数。运行<code>cargo test --help</code>会告诉你<code>cargo test</code>的相关参数，而运行<code>cargo test -- --help</code>则会告诉你位于分隔符<code>--</code>之后的相关参数。</p>
<a class="header" href="#并行或连续的运行测试" name="并行或连续的运行测试"><h3>并行或连续的运行测试</h3></a>
<!-- Are we safe assuming the reader will know enough about threads in this
context? -->
<!-- Yes /Carol -->
<p>当运行多个测试时，他们默认使用线程来并行的运行。这意味着测试会更快的运行完毕，所以可以更快的得到代码能否工作的反馈。因为测试是在同时运行的，你应该小心测试不能相互依赖或任何共享状态，包括类似于当前工作目录或者环境变量这样的共享环境。</p>
<p>例如，每一个测试都运行一些代码在硬盘上创建一个<code>test-output.txt</code>文件并写入一些数据。接着每一个测试都读取文件中的数据并断言这个文件包含特定的值，而这个值在每个测试中都是不同的。因为所有测试都是同时运行的，一个测试可能会在另一个测试读写文件过程中覆盖了文件。那么第二个测试就会失败，并不是因为代码不正确，而是因为测试并行运行时相互干涉。一个解决方案是使每一个测试读写不同的文件；另一个是一次运行一个测试。</p>
<p>如果你不希望测试并行运行，或者想要更加精确的控制使用线程的数量，可以传递<code>--test-threads</code>参数和希望使用线程的数量给测试二进制文件。例如：</p>
<pre><code>$ cargo test -- --test-threads=1
</code></pre>
<p>这里将测试线程设置为 1，告诉程序不要使用任何并行机制。这也会比并行运行花费更多时间，不过测试就不会在存在共享状态时潜在的相互干涉了。</p>
<a class="header" href="#显示测试输出" name="显示测试输出"><h3>显示测试输出</h3></a>
<p>如果测试通过了，Rust 的测试库默认会捕获打印到标准输出的任何内容。例如，如果在测试中调用<code>println!</code>而测试通过了，我们将不会在终端看到<code>println!</code>的输出：只会看到说明测试通过的行。如果测试失败了，就会看到任何标准输出和其他错误信息。</p>
<p>例如，列表 11-20 有一个无意义的函数它打印出其参数的值并接着返回 10。接着还有一个会通过的测试和一个会失败的测试：</p>
<p><span class="filename">Filename: src/lib.rs</span></p>
<pre><code class="language-rust">fn prints_and_returns_10(a: i32) -&gt; i32 {
println!(&quot;I got the value {}&quot;, a);
10
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn this_test_will_pass() {
let value = prints_and_returns_10(4);
assert_eq!(10, value);
}
#[test]
fn this_test_will_fail() {
let value = prints_and_returns_10(8);
assert_eq!(5, value);
}
}
</code></pre>
<p><span class="caption">Listing 11-10: Tests for a function that calls <code>println!</code>
</span></p>
<p>运行<code>cargo test</code>将会看到这些测试的输出：</p>
<pre><code>running 2 tests
test tests::this_test_will_pass ... ok
test tests::this_test_will_fail ... FAILED
failures:
---- tests::this_test_will_fail stdout ----
I got the value 8
thread 'tests::this_test_will_fail' panicked at 'assertion failed: `(left ==
right)` (left: `5`, right: `10`)', src/lib.rs:19
note: Run with `RUST_BACKTRACE=1` for a backtrace.
failures:
tests::this_test_will_fail
test result: FAILED. 1 passed; 1 failed; 0 ignored; 0 measured
</code></pre>
<p>注意输出中哪里也不会出现<code>I got the value 4</code>，这是当测试通过时打印的内容。这些输出被捕获。失败测试的输出，<code>I got the value 8</code>，则出现在输出的测试总结部分，它也显示了测试失败的原因。</p>
<p>如果你希望也能看到通过的测试中打印的值，捕获输出的行为可以通过<code>--nocapture</code>参数来禁用：</p>
<pre><code>$ cargo test -- --nocapture
</code></pre>
<p>使用<code>--nocapture</code>参数再次运行列表 11-10 中的测试会显示：</p>
<pre><code>running 2 tests
I got the value 4
I got the value 8
test tests::this_test_will_pass ... ok
thread 'tests::this_test_will_fail' panicked at 'assertion failed: `(left ==
right)` (left: `5`, right: `10`)', src/lib.rs:19
note: Run with `RUST_BACKTRACE=1` for a backtrace.
test tests::this_test_will_fail ... FAILED
failures:
failures:
tests::this_test_will_fail
test result: FAILED. 1 passed; 1 failed; 0 ignored; 0 measured
</code></pre>
<p>注意测试的输出和测试结果的输出是相互交叉的；这是由于上一部分讲到的测试是并行运行的。尝试一同使用<code>--test-threads=1</code>和<code>--nocapture</code>功能来看看输出是什么样子！</p>
<a class="header" href="#通过名称来运行测试的子集" name="通过名称来运行测试的子集"><h3>通过名称来运行测试的子集</h3></a>
<p>有时运行整个测试集会耗费很多时间。如果你负责特定位置的代码，你可能会希望只与这些代码相关的测试。可以向<code>cargo test</code>传递希望运行的测试的（部分）名称作为参数来选择运行哪些测试。</p>
<p>为了展示如何运行测试的子集，列表 11-11 使用<code>add_two</code>函数创建了三个测试来供我们选择运行哪一个：</p>
<p><span class="filename">Filename: src/lib.rs</span></p>
<pre><code class="language-rust">pub fn add_two(a: i32) -&gt; i32 {
a + 2
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn add_two_and_two() {
assert_eq!(4, add_two(2));
}
#[test]
fn add_three_and_two() {
assert_eq!(5, add_two(3));
}
#[test]
fn one_hundred() {
assert_eq!(102, add_two(100));
}
}
</code></pre>
<p><span class="caption">Listing 11-11: Three tests with a variety of names</span></p>
<p>如果没有传递任何参数就运行测试，如你所见，所有测试都会并行运行：</p>
<pre><code>running 3 tests
test tests::add_two_and_two ... ok
test tests::add_three_and_two ... ok
test tests::one_hundred ... ok
test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured
</code></pre>
<a class="header" href="#运行单个测试" name="运行单个测试"><h4>运行单个测试</h4></a>
<p>可以向<code>cargo test</code>传递任意测试的名称来只运行这个测试：</p>
<pre><code>$ cargo test one_hundred
Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs
Running target/debug/deps/adder-06a75b4a1f2515e9
running 1 test
test tests::one_hundred ... ok
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured
</code></pre>
<p>不能像这样指定多个测试名称，只有传递给<code>cargo test</code>的第一个值才会被使用。</p>
<a class="header" href="#过滤运行多个测试" name="过滤运行多个测试"><h4>过滤运行多个测试</h4></a>
<p>然而，可以指定测试的部分名称，这样任何名称匹配这个值的测试会被运行。例如，因为头两个测试的名称包含<code>add</code>，可以通过<code>cargo test add</code>来运行这两个测试：</p>
<pre><code>$ cargo test add
Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs
Running target/debug/deps/adder-06a75b4a1f2515e9
running 2 tests
test tests::add_two_and_two ... ok
test tests::add_three_and_two ... ok
test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured
</code></pre>
<p>这运行了所有名字中带有<code>add</code>的测试。同时注意测试所在的模块作为测试名称的一部分，所以可以通过模块名来过滤运行一个模块中的所有测试。</p>
<!-- in what kind of situation might you need to run only some tests, when you
have lots and lots in a program? -->
<!-- We covered this in the first paragraph of the "Running a Subset of Tests
by Name" section, do you think it should be repeated so soon? Most people who
use tests have sufficient motivation for wanting to run a subset of the tests,
they just need to know how to do it with Rust, so we don't think this is a
point that needs to be emphasized multiple times. /Carol -->
<a class="header" href="#除非指定否则忽略某些测试" name="除非指定否则忽略某些测试"><h3>除非指定否则忽略某些测试</h3></a>
<p>有时一些特定的测试执行起来是非常耗费时间的，所以在运行大多数<code>cargo test</code>的时候希望能排除他们。与其通过参数列举出所有希望运行的测试，也可以使用<code>ignore</code>属性来标记耗时的测试来排除他们：</p>
<p><span class="filename">Filename: src/lib.rs</span></p>
<pre><code class="language-rust">#[test]
fn it_works() {
assert!(true);
}
#[test]
#[ignore]
fn expensive_test() {
// code that takes an hour to run
}
</code></pre>
<p>我们对想要排除的测试的<code>#[test]</code>之后增加了<code>#[ignore]</code>行。现在如果运行测试，就会发现<code>it_works</code>运行了，而<code>expensive_test</code>没有运行：</p>
<pre><code>$ cargo test
Compiling adder v0.1.0 (file:///projects/adder)
Finished debug [unoptimized + debuginfo] target(s) in 0.24 secs
Running target/debug/deps/adder-ce99bcc2479f4607
running 2 tests
test expensive_test ... ignored
test it_works ... ok
test result: ok. 1 passed; 0 failed; 1 ignored; 0 measured
Doc-tests adder
running 0 tests
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured
</code></pre>
<p><code>expensive_test</code>被列为<code>ignored</code>，如果只希望运行被忽略的测试，可以使用<code>cargo test -- --ignored</code>来请求运行他们：</p>
<!-- what does the double `-- --` mean? That seems interesting -->
<!-- We covered that in the second paragraph after the "Controlling How Tests
are Run" heading, and this section is beneath that heading, so I don't think a
back reference is needed /Carol -->
<!-- is that right, this way the program knows to run only the test with
`ignore` if we add this, or it knows to run all tests? -->
<!-- Is this unclear from the output that shows `expensive_test` was run and
the `it_works` test does not appear? I'm not sure how to make this clearer.
/Carol -->
<pre><code class="language-text">$ cargo test -- --ignored
Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs
Running target/debug/deps/adder-ce99bcc2479f4607
running 1 test
test expensive_test ... ok
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured
</code></pre>
<p>通过控制运行哪些测试，可以确保运行<code>cargo test</code>的结果是快速的。当某个时刻需要检查<code>ignored</code>测试的结果而且你也有时间等待这个结果的话，可以选择执行<code>cargo test -- --ignored</code>。</p>
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