feat: replace end2end test and add more test

tests/if-else.test

@@ -0,0 +1,22 @@
+[expected_return_code]
+0
+
+[code]
+fn min(a: i32, b: i32) -> i32 {
+    if a < b {
+        return a;
+    } else {
+        return b;
+    }
+}
+
+[harness]
+extern int min(int a, int b);
+
+int main() {
+    if (min(12, 15)) {
+        return 0;
+    } else {
+        return -1;
+    }
+}