tests: move t0009-prio-queue.sh to the new unit testing framework

t/t0009-prio-queue.sh along with t/helper/test-prio-queue.c unit
tests Git's implementation of a priority queue. Migrate the
test over to the new unit testing framework to simplify debugging
and reduce test run-time. Refactor the required logic and add
a new test case in addition to porting over the original ones in
shell.

Signed-off-by: Chandra Pratap <chandrapratap3519@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/unit-tests/t-prio-queue.c

@@ -0,0 +1,98 @@
+#include "test-lib.h"
+#include "prio-queue.h"
+
+static int intcmp(const void *va, const void *vb, void *data UNUSED)
+{
+	const int *a = va, *b = vb;
+	return *a - *b;
+}
+
+
+#define MISSING  -1
+#define DUMP	 -2
+#define STACK	 -3
+#define GET	 -4
+#define REVERSE  -5
+
+static int show(int *v)
+{
+	return v ? *v : MISSING;
+}
+
+static void test_prio_queue(int *input, int *result, size_t input_size)
+{
+	struct prio_queue pq = { intcmp };
+
+	for (int i = 0, j = 0; i < input_size; i++) {
+		void *peek, *get;
+		switch(input[i]) {
+		case GET:
+			peek = prio_queue_peek(&pq);
+			get = prio_queue_get(&pq);
+			if (!check(peek == get))
+				return;
+			if(!check_int(result[j++], ==, show(get)))
+				test_msg("failed at result[] index %d", j-1);
+			break;
+		case DUMP:
+			while ((peek = prio_queue_peek(&pq))) {
+				get = prio_queue_get(&pq);
+				if (!check(peek == get))
+					return;
+				if(!check_int(result[j++], ==, show(get)))
+					test_msg("failed at result[] index %d", j-1);
+			}
+			break;
+		case STACK:
+			pq.compare = NULL;
+			break;
+		case REVERSE:
+			prio_queue_reverse(&pq);
+			break;
+		default:
+			prio_queue_put(&pq, &input[i]);
+			break;
+		}
+	}
+	clear_prio_queue(&pq);
+}
+
+#define BASIC_INPUT 2, 6, 3, 10, 9, 5, 7, 4, 5, 8, 1, DUMP
+#define BASIC_RESULT 1, 2, 3, 4, 5, 5, 6, 7, 8, 9, 10
+
+#define MIXED_PUT_GET_INPUT 6, 2, 4, GET, 5, 3, GET, GET, 1, DUMP
+#define MIXED_PUT_GET_RESULT 2, 3, 4, 1, 5, 6
+
+#define EMPTY_QUEUE_INPUT 1, 2, GET, GET, GET, 1, 2, GET, GET, GET
+#define EMPTY_QUEUE_RESULT 1, 2, MISSING, 1, 2, MISSING
+
+#define STACK_INPUT STACK, 8, 1, 5, 4, 6, 2, 3, DUMP
+#define STACK_RESULT 3, 2, 6, 4, 5, 1, 8
+
+#define REVERSE_STACK_INPUT STACK, 1, 2, 3, 4, 5, 6, REVERSE, DUMP
+#define REVERSE_STACK_RESULT 1, 2, 3, 4, 5, 6
+
+#define TEST_INPUT(INPUT, RESULT, name)			\
+  static void test_##name(void)				\
+{								\
+	int input[] = {INPUT};					\
+	int result[] = {RESULT};				\
+	test_prio_queue(input, result, ARRAY_SIZE(input));	\
+}
+
+TEST_INPUT(BASIC_INPUT, BASIC_RESULT, basic)
+TEST_INPUT(MIXED_PUT_GET_INPUT, MIXED_PUT_GET_RESULT, mixed)
+TEST_INPUT(EMPTY_QUEUE_INPUT, EMPTY_QUEUE_RESULT, empty)
+TEST_INPUT(STACK_INPUT, STACK_RESULT, stack)
+TEST_INPUT(REVERSE_STACK_INPUT, REVERSE_STACK_RESULT, reverse)
+
+int cmd_main(int argc, const char **argv)
+{
+	TEST(test_basic(), "prio-queue works for basic input");
+	TEST(test_mixed(), "prio-queue works for mixed put & get commands");
+	TEST(test_empty(), "prio-queue works when queue is empty");
+	TEST(test_stack(), "prio-queue works when used as a LIFO stack");
+	TEST(test_reverse(), "prio-queue works when LIFO stack is reversed");
+
+	return test_done();
+}