From 3dcc9098033b5c38f849a0fef419d4e43caea69c Mon Sep 17 00:00:00 2001
From: jzmaddock <john@johnmaddock.co.uk>
Date: Thu, 22 Feb 2024 11:56:17 +0000
Subject: [PATCH] Chebyshev coverage improvements.

---
 include/boost/math/special_functions/binomial.hpp |  2 +-
 test/chebyshev_test.cpp                           |  7 +++++++
 test/math_unit_test.hpp                           | 14 ++++++++++++++
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/include/boost/math/special_functions/binomial.hpp b/include/boost/math/special_functions/binomial.hpp
index 2220b2364..e776a90bb 100644
--- a/include/boost/math/special_functions/binomial.hpp
+++ b/include/boost/math/special_functions/binomial.hpp
@@ -26,7 +26,7 @@ T binomial_coefficient(unsigned n, unsigned k, const Policy& pol)
    static const char* function = "boost::math::binomial_coefficient<%1%>(unsigned, unsigned)";
    if(k > n)
       return policies::raise_domain_error<T>(function, "The binomial coefficient is undefined for k > n, but got k = %1%.", static_cast<T>(k), pol);
-   T result;
+   T result;  // LCOV_EXCL_LINE
    if((k == 0) || (k == n))
       return static_cast<T>(1);
    if((k == 1) || (k == n-1))
diff --git a/test/chebyshev_test.cpp b/test/chebyshev_test.cpp
index be9323f2b..84117718c 100644
--- a/test/chebyshev_test.cpp
+++ b/test/chebyshev_test.cpp
@@ -85,6 +85,13 @@ void test_clenshaw_recurrence()
     std::array<Real, 6> c5 = { {0, 0, 0, 0, 0, 1} };
     std::array<Real, 7> c6 = { {0, 0, 0, 0, 0, 0, 1} };
 
+    //
+    // Error handling checks:
+    //
+    CHECK_THROW(chebyshev_clenshaw_recurrence(c0.data(), c0.size(), Real(-1), Real(1), Real(-2)), std::domain_error);
+    CHECK_THROW(chebyshev_clenshaw_recurrence(c0.data(), c0.size(), Real(-1), Real(1), Real(2)), std::domain_error);
+    CHECK_EQUAL(chebyshev_clenshaw_recurrence(c0.data(), 0, Real(-1), Real(1), Real(0.5)), Real(0));
+
     Real x = -1;
     // It's not clear from this test which one is more accurate; higher precision cast testing is required, and is done elsewhere:
     int ulps = 50;
diff --git a/test/math_unit_test.hpp b/test/math_unit_test.hpp
index 9554c38a5..648f7de9c 100644
--- a/test/math_unit_test.hpp
+++ b/test/math_unit_test.hpp
@@ -377,6 +377,18 @@ bool check_true(bool condition, std::string const & filename, std::string const
   return true;
 }
 
+void report_non_throw(const std::string& file, int line)
+{
+   std::cerr << "Expected exception not thrown in test at: " << file << ":" << line << std::endl;
+   ++detail::global_error_count;
+}
+
+void report_incorrect_throw(const std::string& file, int line)
+{
+   std::cerr << "Exception of the wrong type thrown in test at: " << file << ":" << line << std::endl;
+   ++detail::global_error_count;
+}
+
 int report_errors()
 {
     if (detail::global_error_count > 0)
@@ -418,4 +430,6 @@ int report_errors()
 
 #define CHECK_TRUE(X) boost::math::test::check_true((X), __FILE__, __func__, __LINE__)
 
+#define CHECK_THROW(x, what) try{ x; boost::math::test::report_non_throw(__FILE__, __LINE__); }catch(const what&){} catch(...){ boost::math::test::report_incorrect_throw(__FILE__, __LINE__); }
+
 #endif