test: add lightweight assertion test harness

tests/testHarness.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <cmath>
+#include <functional>
+#include <string>
+#include <vector>
+
+namespace vftest {
+
+struct TestCase {
+    std::string name;
+    std::function<void()> fn;
+};
+
+std::vector<TestCase>& registry();
+int registerTest(const char* name, std::function<void()> fn);
+void reportCheck(bool ok, const char* expr, const char* file, int line);
+
+extern int failures;
+extern int checks;
+
+} // namespace vftest
+
+#define VF_TEST(name)                                                     \
+    static void name();                                                   \
+    static int name##Registration = vftest::registerTest(#name, name);    \
+    static void name()
+
+#define CHECK(cond) vftest::reportCheck((cond), #cond, __FILE__, __LINE__)
+#define CHECK_EQ(a, b) vftest::reportCheck((a) == (b), #a " == " #b, __FILE__, __LINE__)
+#define CHECK_NEAR(a, b, eps) \
+    vftest::reportCheck(std::fabs((a) - (b)) <= (eps), #a " ~= " #b, __FILE__, __LINE__)