Add IsNaN matcher

17 files changed, 178 insertions, 21 deletions

diff --git a/docs/matchers.md b/docs/matchers.md
index dda49110..d2a2f3c1 100644
--- a/docs/matchers.md
+++ b/docs/matchers.md
@@ -141,18 +141,27 @@ are a permutation of the ones in `some_vec`.
 
 ### Floating point matchers
 
-Catch2 provides 3 matchers that target floating point numbers. These
+Catch2 provides 4 matchers that target floating point numbers. These
 are:
 
 * `WithinAbs(double target, double margin)`,
 * `WithinULP(FloatingPoint target, uint64_t maxUlpDiff)`, and
 * `WithinRel(FloatingPoint target, FloatingPoint eps)`.
+* `IsNaN()`
 
 > `WithinRel` matcher was introduced in Catch2 2.10.0
 
-For more details, read [the docs on comparing floating point
+> `IsNaN` matcher was introduced in Catch2 X.Y.Z.
+
+The first three serve to compare two floating pointe numbers. For more
+details about how they work, read [the docs on comparing floating point
 numbers](comparing-floating-point-numbers.md#floating-point-matchers).
 
+`IsNaN` then does exactly what it says on the tin. It matches the input
+if it is a NaN (Not a Number). The advantage of using it over just plain
+`REQUIRE(std::isnan(x))`, is that if the check fails, with `REQUIRE` you
+won't see the value of `x`, but with `REQUIRE_THAT(x, IsNaN())`, you will.
+
 
 ### Miscellaneous matchers
 
diff --git a/src/catch2/matchers/catch_matchers_floating_point.cpp b/src/catch2/matchers/catch_matchers_floating_point.cpp
index 719fb51f..6e596466 100644
--- a/src/catch2/matchers/catch_matchers_floating_point.cpp
+++ b/src/catch2/matchers/catch_matchers_floating_point.cpp
@@ -225,5 +225,17 @@ WithinRelMatcher WithinRel(float target) {
 }
 
 
-} // namespace Matchers
+
+bool IsNaNMatcher::match( double const& matchee ) const {
+    return std::isnan( matchee );
+}
+
+std::string IsNaNMatcher::describe() const {
+    using namespace std::string_literals;
+    return "is NaN"s;
+}
+
+IsNaNMatcher IsNaN() { return IsNaNMatcher(); }
+
+    } // namespace Matchers
 } // namespace Catch
diff --git a/src/catch2/matchers/catch_matchers_floating_point.hpp b/src/catch2/matchers/catch_matchers_floating_point.hpp
index abdaf159..76816633 100644
--- a/src/catch2/matchers/catch_matchers_floating_point.hpp
+++ b/src/catch2/matchers/catch_matchers_floating_point.hpp
@@ -27,6 +27,11 @@ namespace Matchers {
         double m_margin;
     };
 
+    //! Creates a matcher that accepts numbers within certain range of target
+    WithinAbsMatcher WithinAbs( double target, double margin );
+
+
+
     class WithinUlpsMatcher final : public MatcherBase<double> {
     public:
         WithinUlpsMatcher( double target,
@@ -40,6 +45,13 @@ namespace Matchers {
         Detail::FloatingPointKind m_type;
     };
 
+    //! Creates a matcher that accepts doubles within certain ULP range of target
+    WithinUlpsMatcher WithinULP(double target, uint64_t maxUlpDiff);
+    //! Creates a matcher that accepts floats within certain ULP range of target
+    WithinUlpsMatcher WithinULP(float target, uint64_t maxUlpDiff);
+
+
+
     // Given IEEE-754 format for floats and doubles, we can assume
     // that float -> double promotion is lossless. Given this, we can
     // assume that if we do the standard relative comparison of
@@ -56,13 +68,6 @@ namespace Matchers {
         double m_epsilon;
     };
 
-    //! Creates a matcher that accepts doubles within certain ULP range of target
-    WithinUlpsMatcher WithinULP(double target, uint64_t maxUlpDiff);
-    //! Creates a matcher that accepts floats within certain ULP range of target
-    WithinUlpsMatcher WithinULP(float target, uint64_t maxUlpDiff);
-    //! Creates a matcher that accepts numbers within certain range of target
-    WithinAbsMatcher WithinAbs(double target, double margin);
-
     //! Creates a matcher that accepts doubles within certain relative range of target
     WithinRelMatcher WithinRel(double target, double eps);
     //! Creates a matcher that accepts doubles within 100*DBL_EPS relative range of target
@@ -72,6 +77,17 @@ namespace Matchers {
     //! Creates a matcher that accepts floats within 100*FLT_EPS relative range of target
     WithinRelMatcher WithinRel(float target);
 
+
+
+    class IsNaNMatcher final : public MatcherBase<double> {
+    public:
+        IsNaNMatcher() = default;
+        bool match( double const& matchee ) const override;
+        std::string describe() const override;
+    };
+
+    IsNaNMatcher IsNaN();
+
 } // namespace Matchers
 } // namespace Catch
 
diff --git a/tests/SelfTest/Baselines/compact.sw.approved.txt b/tests/SelfTest/Baselines/compact.sw.approved.txt
index 1f1622c7..541770cc 100644
--- a/tests/SelfTest/Baselines/compact.sw.approved.txt
+++ b/tests/SelfTest/Baselines/compact.sw.approved.txt
@@ -629,6 +629,7 @@ Matchers.tests.cpp:<line number>: passed: WithinULP( 1., 0 )
 Matchers.tests.cpp:<line number>: passed: WithinRel( 1., 0. )
 Matchers.tests.cpp:<line number>: passed: WithinRel( 1., -0.2 ), std::domain_error
 Matchers.tests.cpp:<line number>: passed: WithinRel( 1., 1. ), std::domain_error
+Matchers.tests.cpp:<line number>: passed: 1., !IsNaN() for: 1.0 not is NaN
 Matchers.tests.cpp:<line number>: passed: 10.f, WithinRel( 11.1f, 0.1f ) for: 10.0f and 11.1 are within 10% of each other
 Matchers.tests.cpp:<line number>: passed: 10.f, !WithinRel( 11.2f, 0.1f ) for: 10.0f not and 11.2 are within 10% of each other
 Matchers.tests.cpp:<line number>: passed: 1.f, !WithinRel( 0.f, 0.99f ) for: 1.0f not and 0 are within 99% of each other
@@ -661,6 +662,7 @@ Matchers.tests.cpp:<line number>: passed: WithinULP( 1.f, static_cast<uint64_t>(
 Matchers.tests.cpp:<line number>: passed: WithinRel( 1.f, 0.f )
 Matchers.tests.cpp:<line number>: passed: WithinRel( 1.f, -0.2f ), std::domain_error
 Matchers.tests.cpp:<line number>: passed: WithinRel( 1.f, 1.f ), std::domain_error
+Matchers.tests.cpp:<line number>: passed: 1., !IsNaN() for: 1.0 not is NaN
 Generators.tests.cpp:<line number>: passed: i % 2 == 0 for: 0 == 0
 Generators.tests.cpp:<line number>: passed: i % 2 == 0 for: 0 == 0
 Generators.tests.cpp:<line number>: passed: i % 2 == 0 for: 0 == 0
@@ -2537,6 +2539,6 @@ InternalBenchmark.tests.cpp:<line number>: passed: q3 == 23. for: 23.0 == 23.0
 Misc.tests.cpp:<line number>: passed:
 Misc.tests.cpp:<line number>: passed:
 test cases:  409 |  309 passed |  84 failed | 5 skipped | 11 failed as expected
-assertions: 2224 | 2047 passed | 145 failed | 32 failed as expected
+assertions: 2226 | 2049 passed | 145 failed | 32 failed as expected
 
 
diff --git a/tests/SelfTest/Baselines/compact.sw.multi.approved.txt b/tests/SelfTest/Baselines/compact.sw.multi.approved.txt
index 4cfcb1ab..5b292da1 100644
--- a/tests/SelfTest/Baselines/compact.sw.multi.approved.txt
+++ b/tests/SelfTest/Baselines/compact.sw.multi.approved.txt
@@ -627,6 +627,7 @@ Matchers.tests.cpp:<line number>: passed: WithinULP( 1., 0 )
 Matchers.tests.cpp:<line number>: passed: WithinRel( 1., 0. )
 Matchers.tests.cpp:<line number>: passed: WithinRel( 1., -0.2 ), std::domain_error
 Matchers.tests.cpp:<line number>: passed: WithinRel( 1., 1. ), std::domain_error
+Matchers.tests.cpp:<line number>: passed: 1., !IsNaN() for: 1.0 not is NaN
 Matchers.tests.cpp:<line number>: passed: 10.f, WithinRel( 11.1f, 0.1f ) for: 10.0f and 11.1 are within 10% of each other
 Matchers.tests.cpp:<line number>: passed: 10.f, !WithinRel( 11.2f, 0.1f ) for: 10.0f not and 11.2 are within 10% of each other
 Matchers.tests.cpp:<line number>: passed: 1.f, !WithinRel( 0.f, 0.99f ) for: 1.0f not and 0 are within 99% of each other
@@ -659,6 +660,7 @@ Matchers.tests.cpp:<line number>: passed: WithinULP( 1.f, static_cast<uint64_t>(
 Matchers.tests.cpp:<line number>: passed: WithinRel( 1.f, 0.f )
 Matchers.tests.cpp:<line number>: passed: WithinRel( 1.f, -0.2f ), std::domain_error
 Matchers.tests.cpp:<line number>: passed: WithinRel( 1.f, 1.f ), std::domain_error
+Matchers.tests.cpp:<line number>: passed: 1., !IsNaN() for: 1.0 not is NaN
 Generators.tests.cpp:<line number>: passed: i % 2 == 0 for: 0 == 0
 Generators.tests.cpp:<line number>: passed: i % 2 == 0 for: 0 == 0
 Generators.tests.cpp:<line number>: passed: i % 2 == 0 for: 0 == 0
@@ -2526,6 +2528,6 @@ InternalBenchmark.tests.cpp:<line number>: passed: q3 == 23. for: 23.0 == 23.0
 Misc.tests.cpp:<line number>: passed:
 Misc.tests.cpp:<line number>: passed:
 test cases:  409 |  309 passed |  84 failed | 5 skipped | 11 failed as expected
-assertions: 2224 | 2047 passed | 145 failed | 32 failed as expected
+assertions: 2226 | 2049 passed | 145 failed | 32 failed as expected
 
 
diff --git a/tests/SelfTest/Baselines/console.std.approved.txt b/tests/SelfTest/Baselines/console.std.approved.txt
index 46df088e..15d8b024 100644
--- a/tests/SelfTest/Baselines/console.std.approved.txt
+++ b/tests/SelfTest/Baselines/console.std.approved.txt
@@ -1534,5 +1534,5 @@ due to unexpected exception with message:
 
 ===============================================================================
 test cases:  409 |  323 passed |  69 failed | 6 skipped | 11 failed as expected
-assertions: 2207 | 2047 passed | 128 failed | 32 failed as expected
+assertions: 2209 | 2049 passed | 128 failed | 32 failed as expected
 
diff --git a/tests/SelfTest/Baselines/console.sw.approved.txt b/tests/SelfTest/Baselines/console.sw.approved.txt
index fcd9626f..26d5e8f3 100644
--- a/tests/SelfTest/Baselines/console.sw.approved.txt
+++ b/tests/SelfTest/Baselines/console.sw.approved.txt
@@ -4672,6 +4672,18 @@ Matchers.tests.cpp:<line number>: PASSED:
   REQUIRE_THROWS_AS( WithinRel( 1., 1. ), std::domain_error )
 
 -------------------------------------------------------------------------------
+Floating point matchers: double
+  IsNaN
+-------------------------------------------------------------------------------
+Matchers.tests.cpp:<line number>
+...............................................................................
+
+Matchers.tests.cpp:<line number>: PASSED:
+  REQUIRE_THAT( 1., !IsNaN() )
+with expansion:
+  1.0 not is NaN
+
+-------------------------------------------------------------------------------
 Floating point matchers: float
   Relative
 -------------------------------------------------------------------------------
@@ -4865,6 +4877,18 @@ Matchers.tests.cpp:<line number>: PASSED:
   REQUIRE_THROWS_AS( WithinRel( 1.f, 1.f ), std::domain_error )
 
 -------------------------------------------------------------------------------
+Floating point matchers: float
+  IsNaN
+-------------------------------------------------------------------------------
+Matchers.tests.cpp:<line number>
+...............................................................................
+
+Matchers.tests.cpp:<line number>: PASSED:
+  REQUIRE_THAT( 1., !IsNaN() )
+with expansion:
+  1.0 not is NaN
+
+-------------------------------------------------------------------------------
 Generators -- adapters
   Filtering by predicate
   Basic usage
@@ -18208,5 +18232,5 @@ Misc.tests.cpp:<line number>: PASSED:
 
 ===============================================================================
 test cases:  409 |  309 passed |  84 failed | 5 skipped | 11 failed as expected
-assertions: 2224 | 2047 passed | 145 failed | 32 failed as expected
+assertions: 2226 | 2049 passed | 145 failed | 32 failed as expected
 
diff --git a/tests/SelfTest/Baselines/console.sw.multi.approved.txt b/tests/SelfTest/Baselines/console.sw.multi.approved.txt
index 1e9c0677..80b63ab8 100644
--- a/tests/SelfTest/Baselines/console.sw.multi.approved.txt
+++ b/tests/SelfTest/Baselines/console.sw.multi.approved.txt
@@ -4670,6 +4670,18 @@ Matchers.tests.cpp:<line number>: PASSED:
   REQUIRE_THROWS_AS( WithinRel( 1., 1. ), std::domain_error )
 
 -------------------------------------------------------------------------------
+Floating point matchers: double
+  IsNaN
+-------------------------------------------------------------------------------
+Matchers.tests.cpp:<line number>
+...............................................................................
+
+Matchers.tests.cpp:<line number>: PASSED:
+  REQUIRE_THAT( 1., !IsNaN() )
+with expansion:
+  1.0 not is NaN
+
+-------------------------------------------------------------------------------
 Floating point matchers: float
   Relative
 -------------------------------------------------------------------------------
@@ -4863,6 +4875,18 @@ Matchers.tests.cpp:<line number>: PASSED:
   REQUIRE_THROWS_AS( WithinRel( 1.f, 1.f ), std::domain_error )
 
 -------------------------------------------------------------------------------
+Floating point matchers: float
+  IsNaN
+-------------------------------------------------------------------------------
+Matchers.tests.cpp:<line number>
+...............................................................................
+
+Matchers.tests.cpp:<line number>: PASSED:
+  REQUIRE_THAT( 1., !IsNaN() )
+with expansion:
+  1.0 not is NaN
+
+-------------------------------------------------------------------------------
 Generators -- adapters
   Filtering by predicate
   Basic usage
@@ -18197,5 +18221,5 @@ Misc.tests.cpp:<line number>: PASSED:
 
 ===============================================================================
 test cases:  409 |  309 passed |  84 failed | 5 skipped | 11 failed as expected
-assertions: 2224 | 2047 passed | 145 failed | 32 failed as expected
+assertions: 2226 | 2049 passed | 145 failed | 32 failed as expected
 
diff --git a/tests/SelfTest/Baselines/junit.sw.approved.txt b/tests/SelfTest/Baselines/junit.sw.approved.txt
index 58762161..25129349 100644
--- a/tests/SelfTest/Baselines/junit.sw.approved.txt
+++ b/tests/SelfTest/Baselines/junit.sw.approved.txt
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <testsuitesloose text artifact
 >
-  <testsuite name="<exe-name>" errors="17" failures="128" skipped="11" tests="2235" hostname="tbd" time="{duration}" timestamp="{iso8601-timestamp}">
+  <testsuite name="<exe-name>" errors="17" failures="128" skipped="11" tests="2237" hostname="tbd" time="{duration}" timestamp="{iso8601-timestamp}">
     <properties>
       <property name="random-seed" value="1"/>
       <property name="filters" value="&quot;*&quot; ~[!nonportable] ~[!benchmark] ~[approvals]"/>
@@ -694,12 +694,14 @@ at Message.tests.cpp:<line number>
     <testcase classname="<exe-name>.global" name="Floating point matchers: double/ULPs" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Floating point matchers: double/Composed" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Floating point matchers: double/Constructor validation" time="{duration}" status="run"/>
+    <testcase classname="<exe-name>.global" name="Floating point matchers: double/IsNaN" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Floating point matchers: float/Relative" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Floating point matchers: float/Relative/Some subnormal values" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Floating point matchers: float/Margin" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Floating point matchers: float/ULPs" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Floating point matchers: float/Composed" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Floating point matchers: float/Constructor validation" time="{duration}" status="run"/>
+    <testcase classname="<exe-name>.global" name="Floating point matchers: float/IsNaN" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Generators -- adapters/Filtering by predicate/Basic usage" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Generators -- adapters/Filtering by predicate/Throws if there are no matching values" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Generators -- adapters/Shortening a range" time="{duration}" status="run"/>
diff --git a/tests/SelfTest/Baselines/junit.sw.multi.approved.txt b/tests/SelfTest/Baselines/junit.sw.multi.approved.txt
index 1da7a257..6220d8e2 100644
--- a/tests/SelfTest/Baselines/junit.sw.multi.approved.txt
+++ b/tests/SelfTest/Baselines/junit.sw.multi.approved.txt
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <testsuites>
-  <testsuite name="<exe-name>" errors="17" failures="128" skipped="11" tests="2235" hostname="tbd" time="{duration}" timestamp="{iso8601-timestamp}">
+  <testsuite name="<exe-name>" errors="17" failures="128" skipped="11" tests="2237" hostname="tbd" time="{duration}" timestamp="{iso8601-timestamp}">
     <properties>
       <property name="random-seed" value="1"/>
       <property name="filters" value="&quot;*&quot; ~[!nonportable] ~[!benchmark] ~[approvals]"/>
@@ -693,12 +693,14 @@ at Message.tests.cpp:<line number>
     <testcase classname="<exe-name>.global" name="Floating point matchers: double/ULPs" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Floating point matchers: double/Composed" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Floating point matchers: double/Constructor validation" time="{duration}" status="run"/>
+    <testcase classname="<exe-name>.global" name="Floating point matchers: double/IsNaN" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Floating point matchers: float/Relative" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Floating point matchers: float/Relative/Some subnormal values" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Floating point matchers: float/Margin" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Floating point matchers: float/ULPs" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Floating point matchers: float/Composed" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Floating point matchers: float/Constructor validation" time="{duration}" status="run"/>
+    <testcase classname="<exe-name>.global" name="Floating point matchers: float/IsNaN" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Generators -- adapters/Filtering by predicate/Basic usage" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Generators -- adapters/Filtering by predicate/Throws if there are no matching values" time="{duration}" status="run"/>
     <testcase classname="<exe-name>.global" name="Generators -- adapters/Shortening a range" time="{duration}" status="run"/>
diff --git a/tests/SelfTest/Baselines/sonarqube.sw.approved.txt b/tests/SelfTest/Baselines/sonarqube.sw.approved.txt
index 4d1dcf2f..a4e08bd2 100644
--- a/tests/SelfTest/Baselines/sonarqube.sw.approved.txt
+++ b/tests/SelfTest/Baselines/sonarqube.sw.approved.txt
@@ -1172,12 +1172,14 @@ at Matchers.tests.cpp:<line number>
     <testCase name="Floating point matchers: double/ULPs" duration="{duration}"/>
     <testCase name="Floating point matchers: double/Composed" duration="{duration}"/>
     <testCase name="Floating point matchers: double/Constructor validation" duration="{duration}"/>
+    <testCase name="Floating point matchers: double/IsNaN" duration="{duration}"/>
     <testCase name="Floating point matchers: float/Relative" duration="{duration}"/>
     <testCase name="Floating point matchers: float/Relative/Some subnormal values" duration="{duration}"/>
     <testCase name="Floating point matchers: float/Margin" duration="{duration}"/>
     <testCase name="Floating point matchers: float/ULPs" duration="{duration}"/>
     <testCase name="Floating point matchers: float/Composed" duration="{duration}"/>
     <testCase name="Floating point matchers: float/Constructor validation" duration="{duration}"/>
+    <testCase name="Floating point matchers: float/IsNaN" duration="{duration}"/>
     <testCase name="Matchers can be (AllOf) composed with the &amp;&amp; operator" duration="{duration}"/>
     <testCase name="Matchers can be (AnyOf) composed with the || operator" duration="{duration}"/>
     <testCase name="Matchers can be composed with both &amp;&amp; and ||" duration="{duration}"/>
diff --git a/tests/SelfTest/Baselines/sonarqube.sw.multi.approved.txt b/tests/SelfTest/Baselines/sonarqube.sw.multi.approved.txt
index 84ca07d6..c00defae 100644
--- a/tests/SelfTest/Baselines/sonarqube.sw.multi.approved.txt
+++ b/tests/SelfTest/Baselines/sonarqube.sw.multi.approved.txt
@@ -1171,12 +1171,14 @@ at Matchers.tests.cpp:<line number>
     <testCase name="Floating point matchers: double/ULPs" duration="{duration}"/>
     <testCase name="Floating point matchers: double/Composed" duration="{duration}"/>
     <testCase name="Floating point matchers: double/Constructor validation" duration="{duration}"/>
+    <testCase name="Floating point matchers: double/IsNaN" duration="{duration}"/>
     <testCase name="Floating point matchers: float/Relative" duration="{duration}"/>
     <testCase name="Floating point matchers: float/Relative/Some subnormal values" duration="{duration}"/>
     <testCase name="Floating point matchers: float/Margin" duration="{duration}"/>
     <testCase name="Floating point matchers: float/ULPs" duration="{duration}"/>
     <testCase name="Floating point matchers: float/Composed" duration="{duration}"/>
     <testCase name="Floating point matchers: float/Constructor validation" duration="{duration}"/>
+    <testCase name="Floating point matchers: float/IsNaN" duration="{duration}"/>
     <testCase name="Matchers can be (AllOf) composed with the &amp;&amp; operator" duration="{duration}"/>
     <testCase name="Matchers can be (AnyOf) composed with the || operator" duration="{duration}"/>
     <testCase name="Matchers can be composed with both &amp;&amp; and ||" duration="{duration}"/>
diff --git a/tests/SelfTest/Baselines/tap.sw.approved.txt b/tests/SelfTest/Baselines/tap.sw.approved.txt
index 16728b46..920c95fd 100644
--- a/tests/SelfTest/Baselines/tap.sw.approved.txt
+++ b/tests/SelfTest/Baselines/tap.sw.approved.txt
@@ -1190,6 +1190,8 @@ ok {test-number} - WithinRel( 1., 0. )
 ok {test-number} - WithinRel( 1., -0.2 ), std::domain_error
 # Floating point matchers: double
 ok {test-number} - WithinRel( 1., 1. ), std::domain_error
+# Floating point matchers: double
+ok {test-number} - 1., !IsNaN() for: 1.0 not is NaN
 # Floating point matchers: float
 ok {test-number} - 10.f, WithinRel( 11.1f, 0.1f ) for: 10.0f and 11.1 are within 10% of each other
 # Floating point matchers: float
@@ -1254,6 +1256,8 @@ ok {test-number} - WithinRel( 1.f, 0.f )
 ok {test-number} - WithinRel( 1.f, -0.2f ), std::domain_error
 # Floating point matchers: float
 ok {test-number} - WithinRel( 1.f, 1.f ), std::domain_error
+# Floating point matchers: float
+ok {test-number} - 1., !IsNaN() for: 1.0 not is NaN
 # Generators -- adapters
 ok {test-number} - i % 2 == 0 for: 0 == 0
 # Generators -- adapters
@@ -4473,5 +4477,5 @@ ok {test-number} - q3 == 23. for: 23.0 == 23.0
 ok {test-number} -
 # xmlentitycheck
 ok {test-number} -
-1..2235
+1..2237
 
diff --git a/tests/SelfTest/Baselines/tap.sw.multi.approved.txt b/tests/SelfTest/Baselines/tap.sw.multi.approved.txt
index 44d078f7..c0e0c4db 100644
--- a/tests/SelfTest/Baselines/tap.sw.multi.approved.txt
+++ b/tests/SelfTest/Baselines/tap.sw.multi.approved.txt
@@ -1188,6 +1188,8 @@ ok {test-number} - WithinRel( 1., 0. )
 ok {test-number} - WithinRel( 1., -0.2 ), std::domain_error
 # Floating point matchers: double
 ok {test-number} - WithinRel( 1., 1. ), std::domain_error
+# Floating point matchers: double
+ok {test-number} - 1., !IsNaN() for: 1.0 not is NaN
 # Floating point matchers: float
 ok {test-number} - 10.f, WithinRel( 11.1f, 0.1f ) for: 10.0f and 11.1 are within 10% of each other
 # Floating point matchers: float
@@ -1252,6 +1254,8 @@ ok {test-number} - WithinRel( 1.f, 0.f )
 ok {test-number} - WithinRel( 1.f, -0.2f ), std::domain_error
 # Floating point matchers: float
 ok {test-number} - WithinRel( 1.f, 1.f ), std::domain_error
+# Floating point matchers: float
+ok {test-number} - 1., !IsNaN() for: 1.0 not is NaN
 # Generators -- adapters
 ok {test-number} - i % 2 == 0 for: 0 == 0
 # Generators -- adapters
@@ -4462,5 +4466,5 @@ ok {test-number} - q3 == 23. for: 23.0 == 23.0
 ok {test-number} -
 # xmlentitycheck
 ok {test-number} -
-1..2235
+1..2237
 
diff --git a/tests/SelfTest/Baselines/xml.sw.approved.txt b/tests/SelfTest/Baselines/xml.sw.approved.txt
index 97aa7d85..6a0d1587 100644
--- a/tests/SelfTest/Baselines/xml.sw.approved.txt
+++ b/tests/SelfTest/Baselines/xml.sw.approved.txt
@@ -5287,6 +5287,17 @@ C
       </Expression>
       <OverallResults successes="6" failures="0" expectedFailures="0" skipped="false"/>
     </Section>
+    <Section name="IsNaN" filename="tests/<exe-name>/UsageTests/Matchers.tests.cpp" >
+      <Expression success="true" type="REQUIRE_THAT" filename="tests/<exe-name>/UsageTests/Matchers.tests.cpp" >
+        <Original>
+          1., !IsNaN()
+        </Original>
+        <Expanded>
+          1.0 not is NaN
+        </Expanded>
+      </Expression>
+      <OverallResults successes="1" failures="0" expectedFailures="0" skipped="false"/>
+    </Section>
     <OverallResult success="true" skips="0"/>
   </TestCase>
   <TestCase name="Floating point matchers: float" tags="[floating-point][matchers]" filename="tests/<exe-name>/UsageTests/Matchers.tests.cpp" >
@@ -5564,6 +5575,17 @@ C
       </Expression>
       <OverallResults successes="7" failures="0" expectedFailures="0" skipped="false"/>
     </Section>
+    <Section name="IsNaN" filename="tests/<exe-name>/UsageTests/Matchers.tests.cpp" >
+      <Expression success="true" type="REQUIRE_THAT" filename="tests/<exe-name>/UsageTests/Matchers.tests.cpp" >
+        <Original>
+          1., !IsNaN()
+        </Original>
+        <Expanded>
+          1.0 not is NaN
+        </Expanded>
+      </Expression>
+      <OverallResults successes="1" failures="0" expectedFailures="0" skipped="false"/>
+    </Section>
     <OverallResult success="true" skips="0"/>
   </TestCase>
   <TestCase name="Generators -- adapters" tags="[generators][generic]" filename="tests/<exe-name>/UsageTests/Generators.tests.cpp" >
@@ -21181,6 +21203,6 @@ b1!
     </Section>
     <OverallResult success="true" skips="0"/>
   </TestCase>
-  <OverallResults successes="2047" failures="145" expectedFailures="32" skips="11"/>
+  <OverallResults successes="2049" failures="145" expectedFailures="32" skips="11"/>
   <OverallResultsCases successes="309" failures="84" expectedFailures="11" skips="5"/>
 </Catch2TestRun>
diff --git a/tests/SelfTest/Baselines/xml.sw.multi.approved.txt b/tests/SelfTest/Baselines/xml.sw.multi.approved.txt
index aed70cfa..c6ddfc80 100644
--- a/tests/SelfTest/Baselines/xml.sw.multi.approved.txt
+++ b/tests/SelfTest/Baselines/xml.sw.multi.approved.txt
@@ -5287,6 +5287,17 @@ C
       </Expression>
       <OverallResults successes="6" failures="0" expectedFailures="0" skipped="false"/>
     </Section>
+    <Section name="IsNaN" filename="tests/<exe-name>/UsageTests/Matchers.tests.cpp" >
+      <Expression success="true" type="REQUIRE_THAT" filename="tests/<exe-name>/UsageTests/Matchers.tests.cpp" >
+        <Original>
+          1., !IsNaN()
+        </Original>
+        <Expanded>
+          1.0 not is NaN
+        </Expanded>
+      </Expression>
+      <OverallResults successes="1" failures="0" expectedFailures="0" skipped="false"/>
+    </Section>
     <OverallResult success="true" skips="0"/>
   </TestCase>
   <TestCase name="Floating point matchers: float" tags="[floating-point][matchers]" filename="tests/<exe-name>/UsageTests/Matchers.tests.cpp" >
@@ -5564,6 +5575,17 @@ C
       </Expression>
       <OverallResults successes="7" failures="0" expectedFailures="0" skipped="false"/>
     </Section>
+    <Section name="IsNaN" filename="tests/<exe-name>/UsageTests/Matchers.tests.cpp" >
+      <Expression success="true" type="REQUIRE_THAT" filename="tests/<exe-name>/UsageTests/Matchers.tests.cpp" >
+        <Original>
+          1., !IsNaN()
+        </Original>
+        <Expanded>
+          1.0 not is NaN
+        </Expanded>
+      </Expression>
+      <OverallResults successes="1" failures="0" expectedFailures="0" skipped="false"/>
+    </Section>
     <OverallResult success="true" skips="0"/>
   </TestCase>
   <TestCase name="Generators -- adapters" tags="[generators][generic]" filename="tests/<exe-name>/UsageTests/Generators.tests.cpp" >
@@ -21180,6 +21202,6 @@ b1!
     </Section>
     <OverallResult success="true" skips="0"/>
   </TestCase>
-  <OverallResults successes="2047" failures="145" expectedFailures="32" skips="11"/>
+  <OverallResults successes="2049" failures="145" expectedFailures="32" skips="11"/>
   <OverallResultsCases successes="309" failures="84" expectedFailures="11" skips="5"/>
 </Catch2TestRun>
diff --git a/tests/SelfTest/UsageTests/Matchers.tests.cpp b/tests/SelfTest/UsageTests/Matchers.tests.cpp
index b2239572..49e25232 100644
--- a/tests/SelfTest/UsageTests/Matchers.tests.cpp
+++ b/tests/SelfTest/UsageTests/Matchers.tests.cpp
@@ -497,6 +497,9 @@ TEST_CASE( "Floating point matchers: float", "[matchers][floating-point]" ) {
         REQUIRE_THROWS_AS( WithinRel( 1.f, -0.2f ), std::domain_error );
         REQUIRE_THROWS_AS( WithinRel( 1.f, 1.f ), std::domain_error );
     }
+    SECTION( "IsNaN" ) {
+        REQUIRE_THAT( 1., !IsNaN() );
+    }
 }
 
 TEST_CASE( "Floating point matchers: double", "[matchers][floating-point]" ) {
@@ -552,6 +555,9 @@ TEST_CASE( "Floating point matchers: double", "[matchers][floating-point]" ) {
         REQUIRE_THROWS_AS( WithinRel( 1., -0.2 ), std::domain_error );
         REQUIRE_THROWS_AS( WithinRel( 1., 1. ), std::domain_error );
     }
+    SECTION("IsNaN") {
+        REQUIRE_THAT( 1., !IsNaN() );
+    }
 }
 
 TEST_CASE( "Floating point matchers that are problematic in approvals",
@@ -566,6 +572,8 @@ TEST_CASE( "Floating point matchers that are problematic in approvals",
     REQUIRE_THAT( NAN, !WithinRel( NAN ) );
     REQUIRE_THAT( 1., !WithinRel( NAN ) );
     REQUIRE_THAT( NAN, !WithinRel( 1. ) );
+    REQUIRE_THAT( NAN, IsNaN() );
+    REQUIRE_THAT( static_cast<double>(NAN