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|
If you cannot find the answer to your question here, and you have read
[Primer](V1_6_Primer.md) and [AdvancedGuide](V1_6_AdvancedGuide.md), send it to
googletestframework@googlegroups.com.
## Why should I use Google Test instead of my favorite C++ testing framework? ##
First, let us say clearly that we don't want to get into the debate of
which C++ testing framework is **the best**. There exist many fine
frameworks for writing C++ tests, and we have tremendous respect for
the developers and users of them. We don't think there is (or will
be) a single best framework - you have to pick the right tool for the
particular task you are tackling.
We created Google Test because we couldn't find the right combination
of features and conveniences in an existing framework to satisfy _our_
needs. The following is a list of things that _we_ like about Google
Test. We don't claim them to be unique to Google Test - rather, the
combination of them makes Google Test the choice for us. We hope this
list can help you decide whether it is for you too.
* Google Test is designed to be portable: it doesn't require exceptions or RTTI; it works around various bugs in various compilers and environments; etc. As a result, it works on Linux, Mac OS X, Windows and several embedded operating systems.
* Nonfatal assertions (`EXPECT_*`) have proven to be great time savers, as they allow a test to report multiple failures in a single edit-compile-test cycle.
* It's easy to write assertions that generate informative messages: you just use the stream syntax to append any additional information, e.g. `ASSERT_EQ(5, Foo(i)) << " where i = " << i;`. It doesn't require a new set of macros or special functions.
* Google Test automatically detects your tests and doesn't require you to enumerate them in order to run them.
* Death tests are pretty handy for ensuring that your asserts in production code are triggered by the right conditions.
* `SCOPED_TRACE` helps you understand the context of an assertion failure when it comes from inside a sub-routine or loop.
* You can decide which tests to run using name patterns. This saves time when you want to quickly reproduce a test failure.
* Google Test can generate XML test result reports that can be parsed by popular continuous build system like Hudson.
* Simple things are easy in Google Test, while hard things are possible: in addition to advanced features like [global test environments](V1_6_AdvancedGuide.md#Global_Set-Up_and_Tear-Down) and tests parameterized by [values](V1_6_AdvancedGuide.md#value-parameterized-tests) or [types](V1_6_AdvancedGuide.md#typed-tests), Google Test supports various ways for the user to extend the framework -- if Google Test doesn't do something out of the box, chances are that a user can implement the feature using Google Test's public API, without changing Google Test itself. In particular, you can:
* expand your testing vocabulary by defining [custom predicates](V1_6_AdvancedGuide.md#predicate-assertions-for-better-error-messages),
* teach Google Test how to [print your types](V1_6_AdvancedGuide.md#teaching-google-test-how-to-print-your-values),
* define your own testing macros or utilities and verify them using Google Test's [Service Provider Interface](V1_6_AdvancedGuide.md#catching-failures), and
* reflect on the test cases or change the test output format by intercepting the [test events](V1_6_AdvancedGuide.md#extending-google-test-by-handling-test-events).
## I'm getting warnings when compiling Google Test. Would you fix them? ##
We strive to minimize compiler warnings Google Test generates. Before releasing a new version, we test to make sure that it doesn't generate warnings when compiled using its CMake script on Windows, Linux, and Mac OS.
Unfortunately, this doesn't mean you are guaranteed to see no warnings when compiling Google Test in your environment:
* You may be using a different compiler as we use, or a different version of the same compiler. We cannot possibly test for all compilers.
* You may be compiling on a different platform as we do.
* Your project may be using different compiler flags as we do.
It is not always possible to make Google Test warning-free for everyone. Or, it may not be desirable if the warning is rarely enabled and fixing the violations makes the code more complex.
If you see warnings when compiling Google Test, we suggest that you use the `-isystem` flag (assuming your are using GCC) to mark Google Test headers as system headers. That'll suppress warnings from Google Test headers.
## Why should not test case names and test names contain underscore? ##
Underscore (`_`) is special, as C++ reserves the following to be used by
the compiler and the standard library:
1. any identifier that starts with an `_` followed by an upper-case letter, and
1. any identifier that containers two consecutive underscores (i.e. `__`) _anywhere_ in its name.
User code is _prohibited_ from using such identifiers.
Now let's look at what this means for `TEST` and `TEST_F`.
Currently `TEST(TestCaseName, TestName)` generates a class named
`TestCaseName_TestName_Test`. What happens if `TestCaseName` or `TestName`
contains `_`?
1. If `TestCaseName` starts with an `_` followed by an upper-case letter (say, `_Foo`), we end up with `_Foo_TestName_Test`, which is reserved and thus invalid.
1. If `TestCaseName` ends with an `_` (say, `Foo_`), we get `Foo__TestName_Test`, which is invalid.
1. If `TestName` starts with an `_` (say, `_Bar`), we get `TestCaseName__Bar_Test`, which is invalid.
1. If `TestName` ends with an `_` (say, `Bar_`), we get `TestCaseName_Bar__Test`, which is invalid.
So clearly `TestCaseName` and `TestName` cannot start or end with `_`
(Actually, `TestCaseName` can start with `_` -- as long as the `_` isn't
followed by an upper-case letter. But that's getting complicated. So
for simplicity we just say that it cannot start with `_`.).
It may seem fine for `TestCaseName` and `TestName` to contain `_` in the
middle. However, consider this:
```
TEST(Time, Flies_Like_An_Arrow) { ... }
TEST(Time_Flies, Like_An_Arrow) { ... }
```
Now, the two `TEST`s will both generate the same class
(`Time_Files_Like_An_Arrow_Test`). That's not good.
So for simplicity, we just ask the users to avoid `_` in `TestCaseName`
and `TestName`. The rule is more constraining than necessary, but it's
simple and easy to remember. It also gives Google Test some wiggle
room in case its implementation needs to change in the future.
If you violate the rule, there may not be immediately consequences,
but your test may (just may) break with a new compiler (or a new
version of the compiler you are using) or with a new version of Google
Test. Therefore it's best to follow the rule.
## Why is it not recommended to install a pre-compiled copy of Google Test (for example, into /usr/local)? ##
In the early days, we said that you could install
compiled Google Test libraries on `*`nix systems using `make install`.
Then every user of your machine can write tests without
recompiling Google Test.
This seemed like a good idea, but it has a
got-cha: every user needs to compile his tests using the _same_ compiler
flags used to compile the installed Google Test libraries; otherwise
he may run into undefined behaviors (i.e. the tests can behave
strangely and may even crash for no obvious reasons).
Why? Because C++ has this thing called the One-Definition Rule: if
two C++ source files contain different definitions of the same
class/function/variable, and you link them together, you violate the
rule. The linker may or may not catch the error (in many cases it's
not required by the C++ standard to catch the violation). If it
doesn't, you get strange run-time behaviors that are unexpected and
hard to debug.
If you compile Google Test and your test code using different compiler
flags, they may see different definitions of the same
class/function/variable (e.g. due to the use of `#if` in Google Test).
Therefore, for your sanity, we recommend to avoid installing pre-compiled
Google Test libraries. Instead, each project should compile
Google Test itself such that it can be sure that the same flags are
used for both Google Test and the tests.
## How do I generate 64-bit binaries on Windows (using Visual Studio 2008)? ##
(Answered by Trevor Robinson)
Load the supplied Visual Studio solution file, either `msvc\gtest-md.sln` or
`msvc\gtest.sln`. Go through the migration wizard to migrate the
solution and project files to Visual Studio 2008. Select
`Configuration Manager...` from the `Build` menu. Select `<New...>` from
the `Active solution platform` dropdown. Select `x64` from the new
platform dropdown, leave `Copy settings from` set to `Win32` and
`Create new project platforms` checked, then click `OK`. You now have
`Win32` and `x64` platform configurations, selectable from the
|
