239 lines
12 KiB
Plaintext
Generated
239 lines
12 KiB
Plaintext
Generated
<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8">
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<title>Go by Example: Testing</title>
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<link rel=stylesheet href="site.css">
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</head>
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<body>
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<div class="example" id="testing">
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<h2><a href="./">Go by Example</a>: Testing</h2>
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<table>
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<tr>
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<td class="docs">
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<p>Unit testing is an important part of writing
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principled Go programs. The <code>testing</code> package
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provides the tools we need to write unit tests
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and the <code>go test</code> command runs tests.</p>
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</td>
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<td class="code empty leading">
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>For the sake of demonstration, this code is in package
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<code>main</code>, but it could be any package. Testing code
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typically lives in the same package as the code it tests.</p>
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</td>
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<td class="code leading">
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<a href="http://play.golang.org/p/GFuPdlBlyMU"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
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<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kn">import</span> <span class="p">(</span>
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<span class="s">"fmt"</span>
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<span class="s">"testing"</span>
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<span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>We’ll be testing this simple implementation of an
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integer minimum. Typically, the code we’re testing
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would be in a source file named something like
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<code>intutils.go</code>, and the test file for it would then
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be named <code>intutils_test.go</code>.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kd">func</span> <span class="nx">IntMin</span><span class="p">(</span><span class="nx">a</span><span class="p">,</span> <span class="nx">b</span> <span class="kt">int</span><span class="p">)</span> <span class="kt">int</span> <span class="p">{</span>
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<span class="k">if</span> <span class="nx">a</span> <span class="p"><</span> <span class="nx">b</span> <span class="p">{</span>
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<span class="k">return</span> <span class="nx">a</span>
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<span class="p">}</span>
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<span class="k">return</span> <span class="nx">b</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>A test is created by writing a function with a name
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beginning with <code>Test</code>.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kd">func</span> <span class="nx">TestIntMinBasic</span><span class="p">(</span><span class="nx">t</span> <span class="o">*</span><span class="nx">testing</span><span class="p">.</span><span class="nx">T</span><span class="p">)</span> <span class="p">{</span>
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<span class="nx">ans</span> <span class="o">:=</span> <span class="nx">IntMin</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="o">-</span><span class="mi">2</span><span class="p">)</span>
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<span class="k">if</span> <span class="nx">ans</span> <span class="o">!=</span> <span class="o">-</span><span class="mi">2</span> <span class="p">{</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p><code>t.Error*</code> will report test failures but continue
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executing the test. <code>t.Fail*</code> will report test
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failures and stop the test immediately.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">t</span><span class="p">.</span><span class="nx">Errorf</span><span class="p">(</span><span class="s">"IntMin(2, -2) = %d; want -2"</span><span class="p">,</span> <span class="nx">ans</span><span class="p">)</span>
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<span class="p">}</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Writing tests can be repetitive, so it’s idiomatic to
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use a <em>table-driven style</em>, where test inputs and
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expected outputs are listed in a table and a single loop
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walks over them and performs the test logic.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kd">func</span> <span class="nx">TestIntMinTableDriven</span><span class="p">(</span><span class="nx">t</span> <span class="o">*</span><span class="nx">testing</span><span class="p">.</span><span class="nx">T</span><span class="p">)</span> <span class="p">{</span>
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<span class="kd">var</span> <span class="nx">tests</span> <span class="p">=</span> <span class="p">[]</span><span class="kd">struct</span> <span class="p">{</span>
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<span class="nx">a</span><span class="p">,</span> <span class="nx">b</span> <span class="kt">int</span>
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<span class="nx">want</span> <span class="kt">int</span>
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<span class="p">}{</span>
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<span class="p">{</span><span class="mi">0</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">0</span><span class="p">},</span>
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<span class="p">{</span><span class="mi">1</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">},</span>
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<span class="p">{</span><span class="mi">2</span><span class="p">,</span> <span class="o">-</span><span class="mi">2</span><span class="p">,</span> <span class="o">-</span><span class="mi">2</span><span class="p">},</span>
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<span class="p">{</span><span class="mi">0</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</span><span class="p">},</span>
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<span class="p">{</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</span><span class="p">},</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>t.Run enables running “subtests”, one for each
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table entry. These are shown separately
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when executing <code>go test -v</code>.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="k">for</span> <span class="nx">_</span><span class="p">,</span> <span class="nx">tt</span> <span class="o">:=</span> <span class="k">range</span> <span class="nx">tests</span> <span class="p">{</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code">
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<div class="highlight"><pre> <span class="nx">testname</span> <span class="o">:=</span> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Sprintf</span><span class="p">(</span><span class="s">"%d,%d"</span><span class="p">,</span> <span class="nx">tt</span><span class="p">.</span><span class="nx">a</span><span class="p">,</span> <span class="nx">tt</span><span class="p">.</span><span class="nx">b</span><span class="p">)</span>
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<span class="nx">t</span><span class="p">.</span><span class="nx">Run</span><span class="p">(</span><span class="nx">testname</span><span class="p">,</span> <span class="kd">func</span><span class="p">(</span><span class="nx">t</span> <span class="o">*</span><span class="nx">testing</span><span class="p">.</span><span class="nx">T</span><span class="p">)</span> <span class="p">{</span>
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<span class="nx">ans</span> <span class="o">:=</span> <span class="nx">IntMin</span><span class="p">(</span><span class="nx">tt</span><span class="p">.</span><span class="nx">a</span><span class="p">,</span> <span class="nx">tt</span><span class="p">.</span><span class="nx">b</span><span class="p">)</span>
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<span class="k">if</span> <span class="nx">ans</span> <span class="o">!=</span> <span class="nx">tt</span><span class="p">.</span><span class="nx">want</span> <span class="p">{</span>
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<span class="nx">t</span><span class="p">.</span><span class="nx">Errorf</span><span class="p">(</span><span class="s">"got %d, want %d"</span><span class="p">,</span> <span class="nx">ans</span><span class="p">,</span> <span class="nx">tt</span><span class="p">.</span><span class="nx">want</span><span class="p">)</span>
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<span class="p">}</span>
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<span class="p">})</span>
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<span class="p">}</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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</tr>
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</table>
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<table>
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<tr>
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<td class="docs">
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<p>Run all tests in the current project in verbose mode.</p>
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</td>
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<td class="code">
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<div class="highlight"><pre><span class="gp">$</span> go <span class="nb">test</span> -v
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<span class="go">== RUN TestIntMinBasic</span>
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<span class="go">--- PASS: TestIntMinBasic (0.00s)</span>
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<span class="go">=== RUN TestIntMinTableDriven</span>
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<span class="go">=== RUN TestIntMinTableDriven/0,1</span>
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<span class="go">=== RUN TestIntMinTableDriven/1,0</span>
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<span class="go">=== RUN TestIntMinTableDriven/2,-2</span>
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<span class="go">=== RUN TestIntMinTableDriven/0,-1</span>
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<span class="go">=== RUN TestIntMinTableDriven/-1,0</span>
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<span class="go">--- PASS: TestIntMinTableDriven (0.00s)</span>
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<span class="go"> --- PASS: TestIntMinTableDriven/0,1 (0.00s)</span>
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<span class="go"> --- PASS: TestIntMinTableDriven/1,0 (0.00s)</span>
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<span class="go"> --- PASS: TestIntMinTableDriven/2,-2 (0.00s)</span>
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<span class="go"> --- PASS: TestIntMinTableDriven/0,-1 (0.00s)</span>
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<span class="go"> --- PASS: TestIntMinTableDriven/-1,0 (0.00s)</span>
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<span class="go">PASS</span>
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<span class="go">ok examples/testing 0.023s</span>
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</pre></div>
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</td>
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</tr>
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</table>
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<p class="next">
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Next example: <a href="command-line-arguments">Command-Line Arguments</a>.
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</p>
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<p class="footer">
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by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/testing">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
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</p>
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</div>
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<script>
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var codeLines = [];
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codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import (\u000A \"fmt\"\u000A \"testing\"\u000A)\u000A');codeLines.push('func IntMin(a, b int) int {\u000A if a \x3C b {\u000A return a\u000A }\u000A return b\u000A}\u000A');codeLines.push('func TestIntMinBasic(t *testing.T) {\u000A ans :\x3D IntMin(2, -2)\u000A if ans !\x3D -2 {\u000A');codeLines.push(' t.Errorf(\"IntMin(2, -2) \x3D %d; want -2\", ans)\u000A }\u000A}\u000A');codeLines.push('func TestIntMinTableDriven(t *testing.T) {\u000A var tests \x3D []struct {\u000A a, b int\u000A want int\u000A }{\u000A {0, 1, 0},\u000A {1, 0, 0},\u000A {2, -2, -2},\u000A {0, -1, -1},\u000A {-1, 0, -1},\u000A }\u000A');codeLines.push(' for _, tt :\x3D range tests {\u000A');codeLines.push(' testname :\x3D fmt.Sprintf(\"%d,%d\", tt.a, tt.b)\u000A t.Run(testname, func(t *testing.T) {\u000A ans :\x3D IntMin(tt.a, tt.b)\u000A if ans !\x3D tt.want {\u000A t.Errorf(\"got %d, want %d\", ans, tt.want)\u000A }\u000A })\u000A }\u000A}\u000A');codeLines.push('');
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</script>
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