Split off testing API into header, separate from source

This is so I could generate new test units using the same API.

test/test.h

@@ -0,0 +1,47 @@
+/* test.h: Unit test API
+ * Created: 2026-02-04
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary:
+ */
+
+#ifndef TEST_H
+#define TEST_H
+
+#include <alisp/alisp.h>
+
+#define TEST_PASSED() printf("[%s]: Passed\n", __func__)
+#define TEST(COND, ...)      \
+  do                         \
+  {                          \
+    bool cond = (COND);      \
+    if (!cond)               \
+    {                        \
+      printf("\tFAIL: ");    \
+    }                        \
+    else                     \
+    {                        \
+      printf("\tPASS: ");    \
+    }                        \
+    printf("%s => ", #COND); \
+    printf(__VA_ARGS__);     \
+    printf("\n");            \
+    if (!cond)               \
+    {                        \
+      assert(0);             \
+    }                        \
+  } while (0)
+
+#endif
+
+/* Copyright (C) 2026 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the Unlicense for details.
+
+ * You may distribute and modify this code under the terms of the Unlicense,
+ * which you should have received a copy of along with this program.  If not,
+ * please go to <https://unlicense.org/>.
+
+ */