GoogleTest初探(1)

此篇主要了解一下GoogleTest中的断言。

总的来说，GoogleTest中的断言分为两大类：EXPECT_*和ASSERT_*，这两者在测试成功或失败后均会给出测试报告，区别是前者在测试失败后会继续执行下面的测试，而后者在测试失败后会立即终止测试。

 GoogleTest中的比较断言，涉及整型，字符串， 浮点型，布尔型的比较判断

Fatal assertion	Nonfatal assertion	Verifies
ASSERT_TRUE(condition)	EXPECT_TRUE(condition)	condition == true
ASSERT_TRUE(condition)	EXPECT_FALSE(condition)	condition == false
ASSERT_EQ(expected, actual)	EXPECT_EQ(expected, actual)	expected == actual
ASSERT_NE(val1, val2)	EXPECT_NE(val1, val2)	val1 != val2
ASSERT_LE(val1, val2)	EXPECT_LE(val1, val2)	val1 <= val2
ASSERT_LT(val1, val2)	EXPECT_LT(val1, val2)	val1 < val2
ASSERT_GE(val1, val2)	EXPECT_GE(val1, val2)	val1 >= val2
ASSERT_GT(val1, val2)	EXPECT_GT(val1, val2)	val1 > val2
ASSERT_STREQ(expected, actual)	EXPECT_STREQ(expected, actual)	(C-string) expected == actual
ASSERT_STRNE(s1, s2)	EXPECT_STRNE(s1, s2)	(C-string) s1 != s2
ASSERT_STRCASEEQ(s1, s2)	EXPECT_STRCASEEQ(s1, s2)	(C-string) s1 == s2  ignoring case
ASSERT_STRCASENE(s1, s2)	EXPECT_STRCASENE(s1, s2)	(C-string) s1 != s2  ignoring case
ASSERT_FLOAT_EQ(expected, actual)	EXPECT_FLOAT_EQ(expected, actual)	(float) expected == actual
ASSERT_DOUBLE_EQ(expected, actual)	EXPECT_DOUBLE_EQ(expected, actual)	(double) expected == actual
ASSERT_NEAR(val1, val2, abs_error)	EXPECT_NEAR(val1, val2, abs_error)	abs(val1-val2) <= abs_error

异常断言：

Fatal assertion	Nonfatal assertion	Verifies
ASSERT_THROW(statement, exception_type);	EXPECT_THROW(statement, exception_type);	statement throws an exception of the given type
ASSERT_ANY_THROW(statement);	EXPECT_ANY_THROW(statement);	statement throws an exception of any type
ASSERT_NO_THROW(statement);	EXPECT_NO_THROW(statement);	statement doesn't throw any exception

几个特殊的断言（可用于流程控制）

SUCCEED()	一个成功断言
FAIL()	一个失败断言(fatal failure)
ADD_FAILURE()	一个失败断言(nonefatal failure)
ADD_FAILURE_AT(file, line)	在给定的文件的给定行数生成一个失败断言(nonefatal failure)

对于一些待测试的，返回值为bool变量的函数，可以使用以下的断言（n代表参数个数）：

Fatal assertion	Nonfatal assertion	Verifies
ASSERT_PREDn(predn, val1,...);	EXPECT_PREDn(predn, val1,...);	predn(val1,...) is true

另外，可以对测试函数进行一个包装，使用以下断言来判断包装好的函数：

Fatal assertion	Nonefatal assertion	Verifies
ASSERT_PRED_FORMATn(pred_formatn, val1, ...);	EXPECT_PRED_FORMATn(pred_formatn, val1, ...);	pred_formatn(val1, ...) is successful

要求pred_formatn的返回值是AssertionResult， 例子如下：

// Returns true if m and n have no common divisors except 1.
bool MutuallyPrime(int m, int n) { ... }

// Returns the smallest prime common divisor of m and n,
// or 1 when m and n are mutually prime.
int SmallestPrimeCommonDivisor(int m, int n) { ... }

// A predicate-formatter for asserting that two integers are mutually prime.
::testing::AssertionResult AssertMutuallyPrime(const char* m_expr,
                                               const char* n_expr,
                                               int m,
                                               int n) 
{
  if (MutuallyPrime(m, n)) return ::testing::AssertionSuccess();

  return ::testing::AssertionFailure() << m_expr << " and " << n_expr
      << " (" << m << " and " << n << ") are not mutually prime, "
      << "as they have a common divisor " << SmallestPrimeCommonDivisor(m, n);
}

使用一个AssertMutuallyPrime函数来包装一下待测试函数MutuallyPrime。此时再使用断言：

EXPECT_PRED_FORMAT2(AssertMutuallyPrime, b, c);

如果失败，则会打印出失败信息

b and c (4 and 10) are not mutually prime, as they have a common divisor 2.

还有类型断言：

::testing::StaticAssertTypeEq<T1, T2>();

使用这个函数可以判断T1和T2类型是否一致

最后，可以使用gmock中的各种matchers来进行断言：

Fatal assertion	Nonfatal assertion	Verifies
ASSERT_THAT(value, matcher);	EXPECT_THAT(value, matcher);	value matches matcher

matchers 见gmock 的介绍

参考链接：https://github.com/google/googletest/blob/master/googletest/docs/advanced.md