Trompeloeil

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trompe l'oeil noun (Concise Encyclopedia) Style of representation in which a painted object is intended to deceive the viewer into believing it is the object itself...

What is it?

A thread-safe header-only mocking framework for C++11/14 using the Boost Software License 1.0

Documentation

• Integrating with unit test frame works
• Introduction
• How to contribute
• Compiler compatibility
• External tools
• Presentation videos
• Trompeloeil on CppCast
• Cheat Sheet (2*A4)
• Cook Book
• FAQ
• Backward compatibility with earlier versions of C++
• Platform and library support for Trompeloeil
• Reference

Also, follow up with the post on sequencing for examples on how to restrict or relax allowed sequences of matching calls.

Teaser

#include <trompeloeil.hpp>

class Interface
{
public:
  virtual ~Interface() = default;
  virtual bool foo(int, std::string& s) = 0;
  virtual bool bar(int) = 0;
  virtual bool bar(std::string) = 0;
};

void interface_func(Interface*); // function to test

class Mock : public Interface
{
public:
  MAKE_MOCK2(foo, bool(int, std::string&),override);
  MAKE_MOCK1(bar, bool(int),override);
  MAKE_MOCK1(bar, bool(std::string),override);
  MAKE_MOCK0(baz, void()); // not from Interface
};

TEST(exercise_interface_func)
{
  using trompeloeil::_;  // wild card for matching any value
  using trompeloeil::gt; // greater-than match

  Mock m;

  trompeloeil::sequence seq1, seq2;  // control order of matching calls

  int local_var = 0;

  REQUIRE_CALL(m, bar(ANY(int)))     // expect call to m.bar(int)
    .LR_SIDE_EFFECT(local_var = _1)  // set captured variable to value of param
    .RETURN(_1 > 0)                  // return value depending on param value
    .IN_SEQUENCE(seq1)               // must be first match for seq1
    .TIMES(AT_LEAST(1));             // can be called several times

  FORBID_CALL(m, bar(0));            // but m.bar(0) is not allowed

  REQUIRE_CALL(m, bar("word"))       // expect one call to m.bar(std::string)
    .RETURN(true)
    .IN_SEQUENCE(seq2);              // must be first match for seq2

  REQUIRE_CALL(m, foo(gt(2), _))     // expect call to foo(int,std::string&)
    .WITH(_2 == "")                  // with int > 2 and empty string
    .IN_SEQUENCE(seq1, seq2)         // last for both seq1 and seq2
    .SIDE_EFFECT(_2 = "cat")         // and set param string to "cat"
    .RETURN(true);

  interface_func(&m);

  // all the above expectations must be fulfilled here
}

How to contribute

Contributions are most welcome. For new functionality, please file an issue as an enhancement request first, to get a discussion going about how to best implement it. Also for bugfixes, it is good to file an issue, so that others can see what the problem is and when it's solved. Internal changes are normally not mentioned in the ChangeLog - it should typically reflect what a user can see (however, performance improvements and silencing warnings are visible for users.) Feel free to add your name to the copyright blurb.

Compiler compatibility

Trompeloeil is known to work with:

• GCC 4.8.4+, 4.9.3+, 5, 6, 7, 8, 9, 10
• Clang 3.5, 3.6, 3.7, 3.8, 3.9, 4, 5, 6, 7, 8, 9, 10, 11, 12
• Visual Studio 2015, 2017, 2019

Latest patch level releases are assumed in the versions listed above.

Further details on C++11 support, platform and library limitations, may be found in

• Backward compatibility with earlier versions of C++
• Platform and library support for Trompeloeil

External Tools

• ReSharperC++ extension to VisualStudio has a mock generator for Trompeloeil since 2016.2

Videos

• Intro presentation from Stockholm C++ UG (YouTube 34m) (Slides)
• Presentation from NDC{Oslo} (YouTube 52m) (Slides)
• Detailed presentation from ACCU 2017 (YouTube 1h25m) (Slides with extra material)