diff --git a/eqpalg/test/test_harness.h b/eqpalg/test/test_harness.h
new file mode 100644
index 0000000..8e0b8b4
--- /dev/null
+++ b/eqpalg/test/test_harness.h
@@ -0,0 +1,84 @@
+// eqpalg/test/test_harness.h
+#pragma once
+#include <cmath>
+#include <functional>
+#include <iostream>
+#include <sstream>
+#include <stdexcept>
+#include <string>
+#include <vector>
+
+struct TestRunner {
+  struct Case {
+    const char* name;
+    std::function<void()> fn;
+  };
+  inline static std::vector<Case> cases;
+
+  static int run() {
+    int passed = 0, failed = 0;
+    for (auto& c : cases) {
+      std::cout << "  " << c.name << " ... ";
+      try {
+        c.fn();
+        std::cout << "PASSED\n";
+        passed++;
+      } catch (const std::exception& e) {
+        std::cout << "FAILED\n    " << e.what() << "\n";
+        failed++;
+      } catch (...) {
+        std::cout << "FAILED (unknown)\n";
+        failed++;
+      }
+    }
+    std::cout << "\n" << passed << " passed, " << failed << " failed\n";
+    return failed ? 1 : 0;
+  }
+};
+
+struct AutoReg {
+  AutoReg(const char* name, std::function<void()> fn) {
+    TestRunner::cases.push_back({name, std::move(fn)});
+  }
+};
+
+#define TEST(name)                                                             \
+  static void testfn_##name();                                                 \
+  static AutoReg autoreg_##name(#name, testfn_##name);                        \
+  static void testfn_##name()
+
+#define CHECK(expr)                                                            \
+  do {                                                                         \
+    if (!(expr))                                                               \
+      throw std::runtime_error("CHECK(" #expr ") failed");                     \
+  } while (0)
+
+#define CHECK_EQ(a, b)                                                         \
+  do {                                                                         \
+    if ((a) != (b)) {                                                          \
+      std::ostringstream os;                                                   \
+      os << "CHECK_EQ: " << (a) << " != " << (b);                              \
+      throw std::runtime_error(os.str());                                      \
+    }                                                                          \
+  } while (0)
+
+#define CHECK_FLOAT_EQ(a, b, eps)                                              \
+  do {                                                                         \
+    if (std::fabs((a) - (b)) > (eps)) {                                        \
+      std::ostringstream os;                                                   \
+      os << "CHECK_FLOAT_EQ: |" << (a) << " - " << (b) << "| > " << (eps);    \
+      throw std::runtime_error(os.str());                                      \
+    }                                                                          \
+  } while (0)
+
+#define CHECK_THROWS(expr)                                                     \
+  do {                                                                         \
+    bool caught = false;                                                       \
+    try {                                                                      \
+      (void)(expr);                                                            \
+    } catch (...) {                                                            \
+      caught = true;                                                           \
+    }                                                                          \
+    if (!caught)                                                               \
+      throw std::runtime_error("CHECK_THROWS(" #expr ") did not throw");       \
+  } while (0)
diff --git a/eqpalg/test/test_main.cc b/eqpalg/test/test_main.cc
new file mode 100644
index 0000000..9fb8e85
--- /dev/null
+++ b/eqpalg/test/test_main.cc
@@ -0,0 +1,7 @@
+// eqpalg/test/test_main.cc
+#include "test_harness.h"
+
+int main() {
+  std::cout << "ExpressionEngine Tests\n======================\n\n";
+  return TestRunner::run();
+}