Make tests test for accuracy.

1 files changed, 15 insertions, 3 deletions

diff --git a/tests/Euler.cpp b/tests/Euler.cpp
index 5666cd8..0a6e28e 100644
--- a/tests/Euler.cpp
+++ b/tests/Euler.cpp
@@ -2,6 +2,7 @@
 #include <cmath>
 #include <cstdlib>
 #include <iostream>
+#include <iomanip>
 
 // y' = y (y == C*exp(t))
 double
@@ -18,8 +19,19 @@ main()
 
   integrator.integrate(2.0);
 
-  std::cout << integrator.y() << std::endl
-            << std::exp(2.0)  << std::endl;
+  double actual   = integrator.y();
+  double expected = std::exp(2.0);
 
-  return EXIT_SUCCESS;
+  std::cout << std::setprecision(10)
+            << "Numerical: " << actual << std::endl
+            << "Expected:  " << expected  << std::endl;
+
+  double error = std::fabs(expected - actual)/expected;
+  if (error > 0.01) {
+    std::cerr << "Error:     " << 100.0*error << "%" << std::endl;
+    return EXIT_FAILURE;
+  } else {
+    std::cout << "Error:     " << 100.0*error << "%" << std::endl;
+    return EXIT_SUCCESS;
+  }
 }