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| ## Assertion macros |
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| Most test frameworks have a large collection of assertion macros to capture all possible conditional forms (```_EQUALS```, ```_NOTEQUALS```, ```_GREATER_THAN``` etc). |
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| **doctest** is different (but it's like [**Catch**](https://github.com/philsquared/Catch) in this regard). Because it decomposes natural C-style conditional expressions most of these forms are reduced to one or two that you will use all the time. That said there are a rich set of auxiliary macros as well. We'll describe all of these here. |
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| Most of these macros come in two forms: |
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| ## Natural Expressions |
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| The ```REQUIRE``` family of macros tests an expression and aborts the test case if it fails. |
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| The ```CHECK``` family are equivalent but execution continues in the same test case even if the assertion fails. This is useful if you have a series of essentially orthogonal assertions and it is useful to see all the results rather than stopping at the first failure. |
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| The ```WARN``` family will just print the error when the condition is not met - but will not fail the test case. |
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| * **REQUIRE(** _expression_ **)** |
| * **CHECK(** _expression_ **)** |
| * **WARN(** _expression_ **)** |
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| Evaluates the expression and records the result. If an exception is thrown it is caught, reported, and counted as a failure (unless it is a **WARN**). These are the macros you will use most of the time |
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| Examples: |
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| ``` |
| CHECK(str == "string value"); |
| CHECK(thisReturnsTrue()); |
| REQUIRE(i == 42); |
| ``` |
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| * **REQUIRE_FALSE(** _expression_ **)** |
| * **CHECK_FALSE(** _expression_ **)** |
| * **WARN_FALSE(** _expression_ **)** |
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| Evaluates the expression and records the _logical NOT_ of the result. If an exception is thrown it is caught, reported, and counted as a failure. |
| (these forms exist as a workaround for the fact that ! prefixed expressions cannot be decomposed). |
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| Example: |
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| ``` |
| REQUIRE_FALSE(thisReturnsFalse()); |
| ``` |
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| ### Floating point comparisons |
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| When comparing floating point numbers - especially if at least one of them has been computed - great care must be taken to allow for rounding errors and inexact representations. |
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| **doctest** provides a way to perform tolerant comparisons of floating point values through use of a wrapper class called ```doctest::Approx```. ```doctest::Approx``` can be used on either side of a comparison expression. It overloads the comparisons operators to take a tolerance into account. Here's a simple example: |
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| ``` |
| REQUIRE(performComputation() == doctest::Approx(2.1)); |
| ``` |
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| By default a small epsilon value is used that covers many simple cases of rounding errors. When this is insufficient the epsilon value (the amount within which a difference either way is ignored) can be specified by calling the ```epsilon()``` method on the ```doctest::Approx``` instance. e.g.: |
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| ``` |
| REQUIRE(22/7 == doctest::Approx(3.141).epsilon(0.01)); |
| ``` |
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| When dealing with very large or very small numbers it can be useful to specify a scale, which can be achieved by calling the ```scale()``` method on the ```doctest::Approx``` instance. |
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| ## Exceptions |
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| * **REQUIRE_THROWS(** _expression_ **)** |
| * **CHECK_THROWS(** _expression_ **)** |
| * **WARN_THROWS(** _expression_ **)** |
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| Expects that an exception (of any type) is be thrown during evaluation of the expression. |
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| * **REQUIRE_THROWS_AS(** _expression_, _exception type_ **)** |
| * **CHECK_THROWS_AS(** _expression_, _exception type_ **)** |
| * **WARN_THROWS_AS(** _expression_, _exception type_ **)** |
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| Expects that an exception of the _specified type_ is thrown during evaluation of the expression. |
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| * **REQUIRE_NOTHROW(** _expression_ **)** |
| * **CHECK_NOTHROW(** _expression_ **)** |
| * **WARN_NOTHROW(** _expression_ **)** |
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| Expects that no exception is thrown during evaluation of the expression. |
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| -------- |
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| - Check out the [**example**](../../examples/assertion_macros/main.cpp) which shows many of these macros |
| - Do not wrap assertion macros in ```try```/```catch``` - the REQUIRE macros throw exceptions to end the test case execution! |
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| --------------- |
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| [Home](readme.html#reference) |
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