googletest：sample1分析

目录

• 待测文件
• 测试文件
• Test，Test Case, Test Suite
• 小结

待测文件

sample1 包含2个功能：

1. Factorial: 求n!；
2. IsPrime: 判断n是否为素数.

sample1.h

// Returns n! (the factorial of n).  For negative n, n! is defined to be 1.
int Factorial(int n);

// Returns true if and only if n is a prime number.
bool IsPrime(int n);

sample1.cc

#include "sample1.h"

// Returns n! (the factorial of n).  For negative n, n! is defined to be 1.
int Factorial(int n) {
  int result = 1;
  for (int i = 1; i <= n; i++) {
    result *= i;
  }

  return result;
}

// Returns true if and only if n is a prime number.
bool IsPrime(int n) {
  // Trivial case 1: small numbers
  if (n <= 1) return false;

  // Trivial case 2: even numbers
  if (n % 2 == 0) return n == 2;

  // Now, we have that n is odd and n >= 3.

  // Try to divide n by every odd number i, starting from 3
  for (int i = 3;; i += 2) {
    // We only have to try i up to the square root of n
    if (i > n / i) break;

    // Now, we have i <= n/i < n.
    // If n is divisible by i, n is not prime.
    if (n % i == 0) return false;
  }

  // n has no integer factor in the range (1, n), and thus is prime.
  return true;
}

测试文件

sample1_unittest.cc

#include "sample1.h"

#include <limits.h>

#include "gtest/gtest.h"
namespace {

// Tests Factorial().

// Tests factorial of negative numbers.
TEST(FactorialTest, Negative) {
  // This test is named "Negative", and belongs to the "FactorialTest"
  // test case.
  EXPECT_EQ(1, Factorial(-5));
  EXPECT_EQ(1, Factorial(-1));
  EXPECT_GT(Factorial(-10), 0);

  // <TechnicalDetails>
  //
  // EXPECT_EQ(expected, actual) is the same as
  //
  //   EXPECT_TRUE((expected) == (actual))
  //
  // except that it will print both the expected value and the actual
  // value when the assertion fails.  This is very helpful for
  // debugging.  Therefore in this case EXPECT_EQ is preferred.
  //
  // On the other hand, EXPECT_TRUE accepts any Boolean expression,
  // and is thus more general.
  //
  // </TechnicalDetails>
}

// Tests factorial of 0.
TEST(FactorialTest, Zero) { EXPECT_EQ(1, Factorial(0)); }

// Tests factorial of positive numbers.
TEST(FactorialTest, Positive) {
  EXPECT_EQ(1, Factorial(1));
  EXPECT_EQ(2, Factorial(2));
  EXPECT_EQ(6, Factorial(3));
  EXPECT_EQ(40320, Factorial(8));
}

// Tests IsPrime()

// Tests negative input.
TEST(IsPrimeTest, Negative) {
  // This test belongs to the IsPrimeTest test case.

  EXPECT_FALSE(IsPrime(-1));
  EXPECT_FALSE(IsPrime(-2));
  EXPECT_FALSE(IsPrime(INT_MIN));
}

// Tests some trivial cases.
TEST(IsPrimeTest, Trivial) {
  EXPECT_FALSE(IsPrime(0));
  EXPECT_FALSE(IsPrime(1));
  EXPECT_TRUE(IsPrime(2));
  EXPECT_TRUE(IsPrime(3));
}

// Tests positive input.
TEST(IsPrimeTest, Positive) {
  EXPECT_FALSE(IsPrime(4));
  EXPECT_TRUE(IsPrime(5));
  EXPECT_FALSE(IsPrime(6));
  EXPECT_TRUE(IsPrime(23));
}
}  // namespace

对于函数Factorial的测试，定义了测试组件FactorialTest，而每个测试用例对应一个名称. 分别有：

• Negative: 代表输入的n为负数；
• Zero：代表输入的n为0；
• Positive：代表输入的n为正数.

数据检查：

EXPECT_EQ(1, Factorial(-5)); 断言值相等，相当于非致命的assert 1 == Factorial(-5).
EXPECT_GT(Factorial(-10), 0); 断言大小，相当于非致命的assert Factorial(-10) > 0. "<"断言用EXPECT_LT.

对于函数IsPrime的测试，定义了组件IsPrimeTest，每个测试用例对应一个名称，可与FactorialTest组件的测试用例名同名. 分别有：

• Negative: 代表输入的n为负数；
• Trivial: 简单的用例，通常是验证代码基本功能和边界条件；
• Positive：代表输入的n为正数.

Test，Test Case, Test Suite

GoogleTest primer描述如下：

Note: There might be some confusion arising from different definitions of the terms Test, Test Case and Test Suite, so beware of misunderstanding these.

Historically, GoogleTest started to use the term Test Case for grouping related tests, whereas current publications, including International Software Testing Qualifications Board (ISTQB) materials and various textbooks on software quality, use the term Test Suite for this.

The related term Test, as it is used in GoogleTest, corresponds to the term Test Case of ISTQB and others.

The term Test is commonly of broad enough sense, including ISTQB’s definition of Test Case, so it’s not much of a problem here. But the term Test Case as was used in Google Test is of contradictory sense and thus confusing.

GoogleTest recently started replacing the term Test Case with Test Suite. The preferred API is TestSuite. The older TestCase API is being slowly deprecated and refactored away.

So please be aware of the different definitions of the terms:

Meaning	GoogleTest Term	ISTQB Term
Exercise a particular program path with specific input values and verify the results	TEST()	Test Case

大意是：历史上，GoogleTest最开始用TestCase对相关测试进行分组，而ISTQB委员会和教科书都是用的Test Suite表示这个概念. GoogleTest用Test表示对应于ISTQB的Test Case.
GoogleTest最近开始用Test Suite来替换Test Case一词. 首选API是TestSuite，旧的API TestCase开始慢慢被弃用和重构.

GoogleTest中，这是容易混淆的点.

简单说，Googletest中，以前，"Test Case = Test = TEST()"；现在，"Test Case = Test Suite".

ISTQB关于Test Case定义：

A set of preconditions, inputs, actions (where applicable), expected results and postconditions, developed based on test conditions.

小结

TEST用于用户定义测试函数，一个TEST(TestSuiteName, TestName)代表一个测试，TestSuiteName表示测试组件名，TestName表示测试名. 每个测试，都归属一个测试组件；一个测试组件，通常包含多个测试.

注意：
1）用户定义的TestSuiteName和TestName都不应当包含下划线（"_"）；
2）googletest 保证用户定义的测试函数只执行一次；
3）用户编写的测试，其测试结果不应依赖于测试顺序.