Re: [googletest] Is there an easy way of getting the functionality of EXPECT_DOUBLE_EQ from a custom predicate?

[Vlad Losev]

I don't think there is a ready made solution for this case. You can roll your own comparison predicate as described in https://code.google.com/p/googletest/wiki/AdvancedGuide#Using_a_Predicate-Formatter and then define an EXPECT_POINT_EQ macro using it. The algorithm to perform ULP comparison is shown at http://www.cygnus-software.com/papers/comparingfloats/comparingfloats.htm.

HTH,

Vlad

On Thu, Mar 21, 2013 at 4:23 PM, Mike McNees <mmc...@gmail.com> wrote:

In the tests I am working on I very often compare two variables that are structs with doubles in them ie:

typedef struct

{

double i;

double j;

} point;

Instead of always using:

EXPECT_DOUBLE_EQ(point1.i, point2.i);

EXPECT_DOUBLE_EQ(point1.j, point2.j);

I would like to use:

EXPECT_POINT_EQ(point1, point2);

and have a predicate that does the compare, but I would like to have the same 4 ULP bounds. So I am wondering if there is an easy way to use EXPECT_DOUBLE_EQ or even EXPECT_NEAR inside of a predicate? Or will I need to implement that myself? Any ideas?

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[Zhanyong Wan (λx.x x)]

Or, you can use googlemock and define a custom matcher using the stock DoubleEq() matcher, which does the same ULP-based comparison as googletest.

https://code.google.com/p/googlemock/wiki/CheatSheet#Floating-Point_Matchers

using testing::DoubleEq;

using testing::Value;

MATCHER_P(PointEq, rhs, "") {

  return Value(arg.i, DoubleEq(rhs.i)) && Value(arg.j, DoubleEq(rhs.j));

}

...

EXPECT_THAT(point1, PointEq(point2));

--
Zhanyong