From daf5e150da756deb950023d61f0643dac875c941 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@gmail.com>
Date: Wed, 6 Oct 2010 18:50:35 -0400
Subject: Make tests test for accuracy.

---
 tests/Euler.cpp    | 18 +++++++++++++++---
 tests/Midpoint.cpp | 20 ++++++++++++++++----
 tests/RK4.cpp      | 20 ++++++++++++++++----
 3 files changed, 47 insertions(+), 11 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;
+  }
 }
diff --git a/tests/Midpoint.cpp b/tests/Midpoint.cpp
index aea1885..9be7bb7 100644
--- a/tests/Midpoint.cpp
+++ b/tests/Midpoint.cpp
@@ -2,6 +2,7 @@
 #include <cmath>
 #include <cstdlib>
 #include <iostream>
+#include <iomanip>
 
 // y' = y (y == C*exp(t))
 double
@@ -14,12 +15,23 @@ int
 main()
 {
   vZ::MidpointIntegrator integrator(f);
-  integrator.y(1.0).x(0.0).h(0.02);
+  integrator.y(1.0).x(0.0).h(0.01);
 
   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 > 3.4e-5) {
+    std::cerr << "Error:     " << 100.0*error << "%" << std::endl;
+    return EXIT_FAILURE;
+  } else {
+    std::cout << "Error:     " << 100.0*error << "%" << std::endl;
+    return EXIT_SUCCESS;
+  }
 }
diff --git a/tests/RK4.cpp b/tests/RK4.cpp
index 8e0ca0a..7165c76 100644
--- a/tests/RK4.cpp
+++ b/tests/RK4.cpp
@@ -2,6 +2,7 @@
 #include <cmath>
 #include <cstdlib>
 #include <iostream>
+#include <iomanip>
 
 // y' = y (y == C*exp(t))
 double
@@ -14,12 +15,23 @@ int
 main()
 {
   vZ::RK4Integrator integrator(f);
-  integrator.y(1.0).x(0.0).h(0.04);
+  integrator.y(1.0).x(0.0).h(0.01);
 
   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 > 1.7e-10) {
+    std::cerr << "Error:     " << 100.0*error << "%" << std::endl;
+    return EXIT_FAILURE;
+  } else {
+    std::cout << "Error:     " << 100.0*error << "%" << std::endl;
+    return EXIT_SUCCESS;
+  }
 }
-- 
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