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51 lines
1.6 KiB
Markdown
51 lines
1.6 KiB
Markdown
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<a id="top"></a>
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# Data Generators
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_Generators are currently considered an experimental feature and their
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API can change between versions freely._
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Data generators (also known as _data driven/parametrized test cases_)
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let you reuse the same set of assertions across different input values.
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In Catch2, this means that they respect the ordering and nesting
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of the `TEST_CASE` and `SECTION` macros.
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How does combining generators and test cases work might be better
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explained by an example:
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```cpp
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TEST_CASE("Generators") {
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auto i = GENERATE( range(1, 11) );
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SECTION( "Some section" ) {
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auto j = GENERATE( range( 11, 21 ) );
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REQUIRE(i < j);
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}
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}
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```
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the assertion will be checked 100 times, because there are 10 possible
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values for `i` (1, 2, ..., 10) and for each of them, there are 10 possible
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values for `j` (11, 12, ..., 20).
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You can also combine multiple generators by concatenation:
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```cpp
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static int square(int x) { return x * x; }
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TEST_CASE("Generators 2") {
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auto i = GENERATE(0, 1, -1, range(-20, -10), range(10, 20));
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CAPTURE(i);
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REQUIRE(square(i) >= 0);
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}
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```
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This will call `square` with arguments `0`, `1`, `-1`, `-20`, ..., `-11`,
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`10`, ..., `19`.
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----------
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Because of the experimental nature of the current Generator implementation,
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we won't list all of the first-party generators in Catch2. Instead you
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should look at our current usage tests in
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[projects/SelfTest/UsageTests/Generators.tests.cpp](/projects/SelfTest/UsageTests/Generators.tests.cpp).
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For implementing your own generators, you can look at their implementation in
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[include/internal/catch_generators.hpp](/include/internal/catch_generators.hpp).
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