diff --git a/sqlite-vec.c b/sqlite-vec.c
index 1265c18..87ba10a 100644
--- a/sqlite-vec.c
+++ b/sqlite-vec.c
@@ -3427,7 +3427,7 @@ void vec0_free(vec0_vtab *p) {
   }
 }
 
-inline int vec0_num_defined_user_columns(vec0_vtab *p) {
+int vec0_num_defined_user_columns(vec0_vtab *p) {
   return p->numVectorColumns + p->numPartitionColumns;
 }
 
diff --git a/tests/test-unit.c b/tests/test-unit.c
new file mode 100644
index 0000000..107945d
--- /dev/null
+++ b/tests/test-unit.c
@@ -0,0 +1,51 @@
+#include "../sqlite-vec.h"
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+
+#define countof(x) (sizeof(x) / sizeof((x)[0]))
+
+void test_vec0_parse_partition_key_definition() {
+  typedef struct {
+    char * test;
+    int expected_rc;
+    const char *expected_column_name;
+    int expected_column_type;
+  } TestCase;
+
+  TestCase suite[] = {
+    {"user_id integer partition key", SQLITE_OK, "user_id", SQLITE_INTEGER},
+    {"USER_id int partition key", SQLITE_OK, "USER_id", SQLITE_INTEGER},
+    {"category text partition key", SQLITE_OK, "category", SQLITE_TEXT},
+
+    {"", SQLITE_EMPTY, "", 0},
+    {"document_id text primary key", SQLITE_EMPTY, "", 0},
+    {"document_id text partition keyy", SQLITE_EMPTY, "", 0},
+  };
+  for(int i = 0; i < countof(suite); i++) {
+    char * out_column_name;
+    int out_column_name_length;
+    int out_column_type;
+    int rc;
+    rc = vec0_parse_partition_key_definition(
+      suite[i].test,
+      strlen(suite[i].test),
+      &out_column_name,
+      &out_column_name_length,
+      &out_column_type
+    );
+    assert(rc == suite[i].expected_rc);
+
+    if(rc == SQLITE_OK) {
+      assert(out_column_name_length == strlen(suite[i].expected_column_name));
+      assert(strncmp(out_column_name, suite[i].expected_column_name, out_column_name_length) == 0);
+      assert(out_column_type == suite[i].expected_column_type);
+    }
+
+    printf("✅ %s\n", suite[i].test);
+  }
+}
+
+int main() {
+  test_vec0_parse_partition_key_definition();
+}