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</a></div> <!----></nav>  <ul class="sidebar-links"><li><section class="sidebar-group depth-0"><p class="sidebar-heading open"><span>Rust入门教程（八）：编写和运行测试</span> <!----></p> <ul class="sidebar-links sidebar-group-items"><li><a href="/rust_camp_tutorial/Rust%E6%96%87%E6%A1%A3/Rust%E5%85%A5%E9%97%A8%E6%95%99%E7%A8%8B%EF%BC%88%E5%85%AB%EF%BC%89.html#一、测试的使用及演示" class="sidebar-link">一、测试的使用及演示</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header"><a href="/rust_camp_tutorial/Rust%E6%96%87%E6%A1%A3/Rust%E5%85%A5%E9%97%A8%E6%95%99%E7%A8%8B%EF%BC%88%E5%85%AB%EF%BC%89.html#_1-1-测试演示" class="sidebar-link">1.1 测试演示</a></li><li class="sidebar-sub-header"><a href="/rust_camp_tutorial/Rust%E6%96%87%E6%A1%A3/Rust%E5%85%A5%E9%97%A8%E6%95%99%E7%A8%8B%EF%BC%88%E5%85%AB%EF%BC%89.html#_1-2-测试失败" class="sidebar-link">1.2 测试失败</a></li></ul></li><li><a href="/rust_camp_tutorial/Rust%E6%96%87%E6%A1%A3/Rust%E5%85%A5%E9%97%A8%E6%95%99%E7%A8%8B%EF%BC%88%E5%85%AB%EF%BC%89.html#二、断言" class="sidebar-link">二、断言</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header"><a href="/rust_camp_tutorial/Rust%E6%96%87%E6%A1%A3/Rust%E5%85%A5%E9%97%A8%E6%95%99%E7%A8%8B%EF%BC%88%E5%85%AB%EF%BC%89.html#_2-1-使用-assert-宏检查测试结果" class="sidebar-link">2.1 使用 assert! 宏检查测试结果</a></li><li class="sidebar-sub-header"><a href="/rust_camp_tutorial/Rust%E6%96%87%E6%A1%A3/Rust%E5%85%A5%E9%97%A8%E6%95%99%E7%A8%8B%EF%BC%88%E5%85%AB%EF%BC%89.html#_2-2-使用-assert-eq-和-assert-ne-测试相等性" class="sidebar-link">2.2 使用 asserteq! 和 assertne! 测试相等性</a></li></ul></li><li><a href="/rust_camp_tutorial/Rust%E6%96%87%E6%A1%A3/Rust%E5%85%A5%E9%97%A8%E6%95%99%E7%A8%8B%EF%BC%88%E5%85%AB%EF%BC%89.html#三、自定义错误消息" class="sidebar-link">三、自定义错误消息</a><ul class="sidebar-sub-headers"></ul></li></ul></section></li></ul> </aside> <main class="page"> <div class="theme-default-content content__default"><h1 id="rust入门教程-八-编写和运行测试"><a href="#rust入门教程-八-编写和运行测试" class="header-anchor">#</a> Rust入门教程（八）：编写和运行测试</h1> <blockquote><p>这一章主要介绍 Rust 的测试。在 Rust 中，一个测试实际上就是一个函数，用于验证非测试代码的功能是否和预期一致。</p></blockquote> <blockquote><p>测试函数体通常执行下面三个操作，也称 <code>3a</code> 操作：</p> <ol><li>准备数据或状态（arrange）；</li> <li>运行被测试的代码（act）；</li> <li>断言结果（assert）。</li></ol></blockquote> <h2 id="一、测试的使用及演示"><a href="#一、测试的使用及演示" class="header-anchor">#</a> 一、测试的使用及演示</h2> <ul><li>测试函数需要使用 <code>test</code> 属性（attribute）进行标注
<ul><li>attribute 就是一段代码的元数据</li> <li>在函数紧接着上面一行添加 <code>#[test]</code>，就将函数变成测试函数了</li></ul></li> <li>运行测试
<ul><li>使用 <code>cargo test</code> 命令运行所有测试
<ul><li>Rust 会构建一个 Test Runner 可执行文件，会运行标注的 test 函数，并报告运行是否成功</li></ul></li> <li>当使用 cargo 创建 library 项目时，会生成一个 test module，里面有默认的 test 函数
<ul><li>可以添加任意数量的 test module 和 test 函数</li></ul></li></ul></li></ul> <h3 id="_1-1-测试演示"><a href="#_1-1-测试演示" class="header-anchor">#</a> 1.1 测试演示</h3> <p>我们输入命令 <code>cargo new test_demo --lib</code> 创建一个项目，在 <code>lib.rs</code> 文件中看到这样的函数：</p> <div class="language-rust extra-class"><pre class="language-rust"><code><span class="token attribute attr-name">#[cfg(test)]</span>
<span class="token keyword">mod</span> <span class="token module-declaration namespace">tests</span> <span class="token punctuation">{</span>
    <span class="token attribute attr-name">#[test]</span>
    <span class="token keyword">fn</span> <span class="token function-definition function">it_works</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">let</span> result <span class="token operator">=</span> <span class="token number">2</span> <span class="token operator">+</span> <span class="token number">2</span><span class="token punctuation">;</span>
        <span class="token macro property">assert_eq!</span><span class="token punctuation">(</span>result<span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre></div><p>这里 <code>assert_eq!</code> 是一个断言的宏，判断两个数是否相等。</p> <p>然后运行 <code>cargo test</code>，结果如下：</p> <div class="language-rust extra-class"><pre class="language-rust"><code>➜  ~<span class="token operator">/</span>code<span class="token operator">/</span>rust<span class="token operator">/</span>test_demo git<span class="token punctuation">:</span><span class="token punctuation">(</span>master<span class="token punctuation">)</span> ✗ cargo test               
   <span class="token class-name">Compiling</span> test_demo v0<span class="token number">.1</span><span class="token punctuation">.</span><span class="token number">0</span> <span class="token punctuation">(</span><span class="token operator">/</span>home<span class="token operator">/</span>cherry<span class="token operator">/</span>code<span class="token operator">/</span>rust<span class="token operator">/</span>test_demo<span class="token punctuation">)</span>
    <span class="token class-name">Finished</span> test <span class="token punctuation">[</span>unoptimized <span class="token operator">+</span> debuginfo<span class="token punctuation">]</span> <span class="token function">target</span><span class="token punctuation">(</span>s<span class="token punctuation">)</span> <span class="token keyword">in</span> <span class="token number">2</span><span class="token punctuation">.</span>33s
     <span class="token class-name">Running</span> <span class="token function">unittests</span> <span class="token punctuation">(</span>target<span class="token operator">/</span>debug<span class="token operator">/</span>deps<span class="token operator">/</span>test_demo<span class="token operator">-</span>357c557c333f0e0d<span class="token punctuation">)</span>

running <span class="token number">1</span> test
test <span class="token namespace">tests<span class="token punctuation">::</span></span>it_works <span class="token punctuation">...</span> ok

test result<span class="token punctuation">:</span> ok<span class="token punctuation">.</span> <span class="token number">1</span> passed<span class="token punctuation">;</span> <span class="token number">0</span> failed<span class="token punctuation">;</span> <span class="token number">0</span> ignored<span class="token punctuation">;</span> <span class="token number">0</span> measured<span class="token punctuation">;</span> <span class="token number">0</span> filtered out<span class="token punctuation">;</span> finished <span class="token keyword">in</span> <span class="token number">0</span><span class="token punctuation">.</span>00s

   <span class="token class-name">Doc</span><span class="token operator">-</span>tests test_demo

running <span class="token number">0</span> tests

test result<span class="token punctuation">:</span> ok<span class="token punctuation">.</span> <span class="token number">0</span> passed<span class="token punctuation">;</span> <span class="token number">0</span> failed<span class="token punctuation">;</span> <span class="token number">0</span> ignored<span class="token punctuation">;</span> <span class="token number">0</span> measured<span class="token punctuation">;</span> <span class="token number">0</span> filtered out<span class="token punctuation">;</span> finished <span class="token keyword">in</span> <span class="token number">0</span><span class="token punctuation">.</span>00s
</code></pre></div><h3 id="_1-2-测试失败"><a href="#_1-2-测试失败" class="header-anchor">#</a> 1.2 测试失败</h3> <ul><li>测试函数 panic 就表示测试失败</li> <li>每个测试都运行在一个新线程中</li> <li>当主线程看到测试线程挂掉后，那个测试就被标记为失败</li></ul> <p>我们单独编写一个带有 panic 的测试函数，测试结果如下：</p> <div class="language-rust extra-class"><pre class="language-rust"><code><span class="token attribute attr-name">#[cfg(test)]</span>
<span class="token keyword">mod</span> <span class="token module-declaration namespace">tests</span> <span class="token punctuation">{</span>
    <span class="token attribute attr-name">#[test]</span>
    <span class="token keyword">fn</span> <span class="token function-definition function">it_works</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">let</span> result <span class="token operator">=</span> <span class="token number">2</span> <span class="token operator">+</span> <span class="token number">2</span><span class="token punctuation">;</span>
        <span class="token macro property">assert_eq!</span><span class="token punctuation">(</span>result<span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>

    <span class="token attribute attr-name">#[test]</span>
    <span class="token keyword">fn</span> <span class="token function-definition function">another</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token macro property">panic!</span><span class="token punctuation">(</span><span class="token string">&quot;Test Failed!&quot;</span><span class="token punctuation">)</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre></div><div class="language-rust extra-class"><pre class="language-rust"><code>➜  ~<span class="token operator">/</span>code<span class="token operator">/</span>rust<span class="token operator">/</span>test_demo git<span class="token punctuation">:</span><span class="token punctuation">(</span>master<span class="token punctuation">)</span> ✗ cargo test
   <span class="token class-name">Compiling</span> test_demo v0<span class="token number">.1</span><span class="token punctuation">.</span><span class="token number">0</span> <span class="token punctuation">(</span><span class="token operator">/</span>home<span class="token operator">/</span>cherry<span class="token operator">/</span>code<span class="token operator">/</span>rust<span class="token operator">/</span>test_demo<span class="token punctuation">)</span>
    <span class="token class-name">Finished</span> test <span class="token punctuation">[</span>unoptimized <span class="token operator">+</span> debuginfo<span class="token punctuation">]</span> <span class="token function">target</span><span class="token punctuation">(</span>s<span class="token punctuation">)</span> <span class="token keyword">in</span> <span class="token number">0</span><span class="token punctuation">.</span>28s
     <span class="token class-name">Running</span> <span class="token function">unittests</span> <span class="token punctuation">(</span>target<span class="token operator">/</span>debug<span class="token operator">/</span>deps<span class="token operator">/</span>test_demo<span class="token operator">-</span>357c557c333f0e0d<span class="token punctuation">)</span>

running <span class="token number">2</span> tests
test <span class="token namespace">tests<span class="token punctuation">::</span></span>another <span class="token punctuation">...</span> <span class="token constant">FAILED</span>
test <span class="token namespace">tests<span class="token punctuation">::</span></span>it_works <span class="token punctuation">...</span> ok

failures<span class="token punctuation">:</span>

<span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span> <span class="token namespace">tests<span class="token punctuation">::</span></span>another stdout <span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span>
thread <span class="token lifetime-annotation symbol">'tests</span><span class="token punctuation">::</span>another' panicked at <span class="token lifetime-annotation symbol">'Test</span> <span class="token macro property">Failed!</span>'<span class="token punctuation">,</span> src<span class="token operator">/</span>lib<span class="token punctuation">.</span>rs<span class="token punctuation">:</span><span class="token number">11</span><span class="token punctuation">:</span><span class="token number">9</span>
note<span class="token punctuation">:</span> run with `<span class="token constant">RUST_BACKTRACE</span><span class="token operator">=</span><span class="token number">1</span>` environment variable to display a backtrace


failures<span class="token punctuation">:</span>
    <span class="token namespace">tests<span class="token punctuation">::</span></span>another

test result<span class="token punctuation">:</span> <span class="token constant">FAILED</span><span class="token punctuation">.</span> <span class="token number">1</span> passed<span class="token punctuation">;</span> <span class="token number">1</span> failed<span class="token punctuation">;</span> <span class="token number">0</span> ignored<span class="token punctuation">;</span> <span class="token number">0</span> measured<span class="token punctuation">;</span> <span class="token number">0</span> filtered out<span class="token punctuation">;</span> finished <span class="token keyword">in</span> <span class="token number">0</span><span class="token punctuation">.</span>00s

error<span class="token punctuation">:</span> test failed<span class="token punctuation">,</span> to rerun pass '<span class="token operator">-</span><span class="token operator">-</span>lib'
</code></pre></div><h2 id="二、断言"><a href="#二、断言" class="header-anchor">#</a> 二、断言</h2> <h3 id="_2-1-使用-assert-宏检查测试结果"><a href="#_2-1-使用-assert-宏检查测试结果" class="header-anchor">#</a> 2.1 使用 assert! 宏检查测试结果</h3> <ul><li>assert! 来自于标准库，用来确定某个状态是否为 true
<ul><li>如果为 true，表示测试通过</li> <li>如果为 false，则调用 panic! 宏，测试失败</li></ul></li></ul> <p>我们用之前写的一个小例子，判断矩形 r1 是否能容纳矩形 r2（为了简单起见，只判断正着放，而不考虑斜着放进去）。</p> <div class="language-rust extra-class"><pre class="language-rust"><code><span class="token keyword">struct</span> <span class="token type-definition class-name">Rect</span> <span class="token punctuation">{</span>
    x<span class="token punctuation">:</span> <span class="token keyword">u32</span><span class="token punctuation">,</span>
    y<span class="token punctuation">:</span> <span class="token keyword">u32</span><span class="token punctuation">,</span>
<span class="token punctuation">}</span>

<span class="token keyword">impl</span> <span class="token class-name">Rect</span> <span class="token punctuation">{</span>
    <span class="token keyword">fn</span> <span class="token function-definition function">can_hold</span><span class="token punctuation">(</span><span class="token operator">&amp;</span><span class="token keyword">self</span><span class="token punctuation">,</span> other<span class="token punctuation">:</span> <span class="token operator">&amp;</span><span class="token class-name">Rect</span><span class="token punctuation">)</span> <span class="token punctuation">-&gt;</span> <span class="token keyword">bool</span> <span class="token punctuation">{</span>
        <span class="token keyword">let</span> x <span class="token operator">=</span> <span class="token keyword">if</span> other<span class="token punctuation">.</span>x <span class="token operator">&gt;</span> other<span class="token punctuation">.</span>y <span class="token punctuation">{</span> other<span class="token punctuation">.</span>x <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span> other<span class="token punctuation">.</span>y <span class="token punctuation">}</span><span class="token punctuation">;</span>
        <span class="token keyword">let</span> y <span class="token operator">=</span> <span class="token keyword">if</span> other<span class="token punctuation">.</span>x <span class="token operator">&lt;</span> other<span class="token punctuation">.</span>y <span class="token punctuation">{</span> other<span class="token punctuation">.</span>x <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span> other<span class="token punctuation">.</span>y <span class="token punctuation">}</span><span class="token punctuation">;</span>
        <span class="token keyword">self</span><span class="token punctuation">.</span>x <span class="token operator">&gt;</span> x <span class="token operator">&amp;&amp;</span> <span class="token keyword">self</span><span class="token punctuation">.</span>y <span class="token operator">&gt;</span> y
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre></div><p>测试函数：</p> <div class="language-rust extra-class"><pre class="language-rust"><code><span class="token attribute attr-name">#[test]</span>
<span class="token keyword">fn</span> <span class="token function-definition function">larger_can_hold_smaller</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">let</span> r1 <span class="token operator">=</span> <span class="token class-name">Rect</span> <span class="token punctuation">{</span> x<span class="token punctuation">:</span> <span class="token number">12</span><span class="token punctuation">,</span> y<span class="token punctuation">:</span> <span class="token number">8</span> <span class="token punctuation">}</span><span class="token punctuation">;</span>
    <span class="token keyword">let</span> r2 <span class="token operator">=</span> <span class="token class-name">Rect</span> <span class="token punctuation">{</span> x<span class="token punctuation">:</span> <span class="token number">5</span><span class="token punctuation">,</span> y<span class="token punctuation">:</span> <span class="token number">10</span> <span class="token punctuation">}</span><span class="token punctuation">;</span>
    <span class="token macro property">assert!</span><span class="token punctuation">(</span>r1<span class="token punctuation">.</span><span class="token function">can_hold</span><span class="token punctuation">(</span><span class="token operator">&amp;</span>r2<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre></div><p>显然返回是 true，测试通过。</p> <h3 id="_2-2-使用-assert-eq-和-assert-ne-测试相等性"><a href="#_2-2-使用-assert-eq-和-assert-ne-测试相等性" class="header-anchor">#</a> 2.2 使用 assert_eq! 和 assert_ne! 测试相等性</h3> <ul><li>都来自标准库</li> <li>判断两个参数是否相等或不等</li> <li>实际上，它们使用的就是 <code>==</code> 和 <code>!=</code> 运算符</li> <li>如果断言失败，该宏会自动打印出两个参数的值
<ul><li>使用 debug 格式打印参数</li> <li>要求参数实现 PartialEq 和 Debug Traits（所有基本类型和标准库里大部分类型基本都实现了）</li> <li>如果使用 <code>assert!</code> 宏，则只会告知测试结果而不会打印出两个参数的值</li></ul></li></ul> <p>我们再写一个简单的例子，将一个数加 2，判断两个值是否相等。</p> <div class="language-rust extra-class"><pre class="language-rust"><code><span class="token keyword">fn</span> <span class="token function-definition function">add_two</span><span class="token punctuation">(</span>a<span class="token punctuation">:</span> <span class="token keyword">i32</span><span class="token punctuation">)</span> <span class="token punctuation">-&gt;</span> <span class="token keyword">i32</span> <span class="token punctuation">{</span>
    a <span class="token operator">+</span> <span class="token number">2</span>
<span class="token punctuation">}</span>    

<span class="token attribute attr-name">#[test]</span>
<span class="token keyword">pub</span> <span class="token keyword">fn</span> <span class="token function-definition function">it_add_two</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token macro property">assert_eq!</span><span class="token punctuation">(</span><span class="token number">4</span><span class="token punctuation">,</span> <span class="token function">add_two</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre></div><p>结果显然是正确的，若我们更改函数逻辑，把加 2 改成加 3，则运行测试结果为：</p> <div class="language-rust extra-class"><pre class="language-rust"><code>➜  ~<span class="token operator">/</span>code<span class="token operator">/</span>rust<span class="token operator">/</span>test_demo git<span class="token punctuation">:</span><span class="token punctuation">(</span>master<span class="token punctuation">)</span> ✗ cargo test
   <span class="token class-name">Compiling</span> test_demo v0<span class="token number">.1</span><span class="token punctuation">.</span><span class="token number">0</span> <span class="token punctuation">(</span><span class="token operator">/</span>home<span class="token operator">/</span>cherry<span class="token operator">/</span>code<span class="token operator">/</span>rust<span class="token operator">/</span>test_demo<span class="token punctuation">)</span>
    <span class="token class-name">Finished</span> test <span class="token punctuation">[</span>unoptimized <span class="token operator">+</span> debuginfo<span class="token punctuation">]</span> <span class="token function">target</span><span class="token punctuation">(</span>s<span class="token punctuation">)</span> <span class="token keyword">in</span> <span class="token number">0</span><span class="token punctuation">.</span>39s
     <span class="token class-name">Running</span> <span class="token function">unittests</span> <span class="token punctuation">(</span>target<span class="token operator">/</span>debug<span class="token operator">/</span>deps<span class="token operator">/</span>test_demo<span class="token operator">-</span>357c557c333f0e0d<span class="token punctuation">)</span>

running <span class="token number">3</span> tests
test <span class="token namespace">tests<span class="token punctuation">::</span></span>it_add_two <span class="token punctuation">...</span> <span class="token constant">FAILED</span>
test <span class="token namespace">tests<span class="token punctuation">::</span></span>it_works <span class="token punctuation">...</span> ok
test <span class="token namespace">tests<span class="token punctuation">::</span></span>larger_can_hold_smaller <span class="token punctuation">...</span> ok

failures<span class="token punctuation">:</span>

<span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span> <span class="token namespace">tests<span class="token punctuation">::</span></span>it_add_two stdout <span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span>
thread <span class="token lifetime-annotation symbol">'tests</span><span class="token punctuation">::</span>it_add_two' panicked at <span class="token lifetime-annotation symbol">'assertion</span> failed<span class="token punctuation">:</span> `<span class="token punctuation">(</span>left <span class="token operator">==</span> right<span class="token punctuation">)</span>`
  left<span class="token punctuation">:</span> `<span class="token number">4</span>`<span class="token punctuation">,</span>
 right<span class="token punctuation">:</span> `<span class="token number">5</span>`'<span class="token punctuation">,</span> src<span class="token operator">/</span>lib<span class="token punctuation">.</span>rs<span class="token punctuation">:</span><span class="token number">37</span><span class="token punctuation">:</span><span class="token number">9</span>
note<span class="token punctuation">:</span> run with `<span class="token constant">RUST_BACKTRACE</span><span class="token operator">=</span><span class="token number">1</span>` environment variable to display a backtrace


failures<span class="token punctuation">:</span>
    <span class="token namespace">tests<span class="token punctuation">::</span></span>it_add_two

test result<span class="token punctuation">:</span> <span class="token constant">FAILED</span><span class="token punctuation">.</span> <span class="token number">2</span> passed<span class="token punctuation">;</span> <span class="token number">1</span> failed<span class="token punctuation">;</span> <span class="token number">0</span> ignored<span class="token punctuation">;</span> <span class="token number">0</span> measured<span class="token punctuation">;</span> <span class="token number">0</span> filtered out<span class="token punctuation">;</span> finished <span class="token keyword">in</span> <span class="token number">0</span><span class="token punctuation">.</span>00s

error<span class="token punctuation">:</span> test failed<span class="token punctuation">,</span> to rerun pass '<span class="token operator">-</span><span class="token operator">-</span>lib'
</code></pre></div><p>编译器将会自动给出两个参数的值（左值和右值），若将宏改成 <code>assert_ne!</code> 测试结果又将变成正确。</p> <h2 id="三、自定义错误消息"><a href="#三、自定义错误消息" class="header-anchor">#</a> 三、自定义错误消息</h2> <p>TODO</p></div> <footer class="page-edit"><!----> <!----></footer> <!----> </main></div><div class="global-ui"></div></div>
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