Add docs/tests.txt and initial tests.cpp for gamematrix

tests.cpp

@@ -0,0 +1,28 @@
+#include <iostream>
+#include <cmath>
+#include "gamematrix.h"  // anpassen, falls euer Header anders heißt
+
+bool approx(double a, double b, double eps = 1e-6) {
+    return std::fabs(a - b) < eps;
+}
+
+int main() {
+    int failed = 0;
+
+    // Beispiel-Test: Rotation um Z 90°
+    std::array<double,3> v = {1,0,0};
+    auto Rz = rot3D(90, 'z'); // ggf. Namespace anpassen
+    auto result = apply(Rz, v);
+    if (!approx(result[0], 0.0) || !approx(result[1], 1.0)) {
+        std::cout << "Test rot3D(Z,90) failed!\n";
+        failed++;
+    }
+
+    // Ausgabe
+    if (failed == 0)
+        std::cout << "ALL TESTS PASSED ✅\n";
+    else
+        std::cout << failed << " TEST(S) FAILED ❌\n";
+
+    return failed;
+}