tests: lib: min_heap: add test coverage for edge cases

Add missing tests for edge cases (ex. peek on empty heap, push to full
heap, ...) to get to 100% coverage (lines & branches)

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>

Author: kartben

tests/lib/min_heap/src/test_min_heap.c

@@ -125,6 +125,11 @@ ZTEST(min_heap_api, test_insert)
 		ret = min_heap_push(&my_heap_gt, &elements[i]);
 		zassert_ok(ret, "min_heap_push failed");
 	}
+
+	/* Try to push one more element to the now full heap */
+	ret = min_heap_push(&my_heap_gt, &elements[0]);
+	zassert_equal(ret, -ENOMEM, "push on full heap should return -ENOMEM");
+
 	validate_heap_order_gt(&my_heap_gt);
 }
 
@@ -152,6 +157,7 @@ ZTEST(min_heap_api, test_peek_and_pop)
 	zassert_equal(peek_key, pop.key, "Peek/pop error");
 	zassert_equal(pop.key, LOWEST_PRIORITY_LS, "heap error %d", pop.key);
 	validate_heap_order_ls(&runtime_heap);
+	zassert_is_null(min_heap_peek(&runtime_heap), "peek on empty heap should return NULL");
 }
 
 ZTEST(min_heap_api, test_find_and_remove)
@@ -165,13 +171,23 @@ ZTEST(min_heap_api, test_find_and_remove)
 	}
 
 	int target_key = 5;
+	int wrong_key = 100;
 	size_t index;
-	struct data removed, *found;
+	struct data removed, *found, *found_ignore_index, *not_found;
 
 	found = min_heap_find(&my_heap, match_key, &target_key, &index);
+	found_ignore_index = min_heap_find(&my_heap, match_key, &target_key, NULL);
+	not_found = min_heap_find(&my_heap, match_key, &wrong_key, &index);
 
 	zassert_not_null(found, "min_heap_find failure");
+	zassert_not_null(found_ignore_index, "min_heap_find failure");
+	zassert_is_null(not_found, "min_heap_find failure");
+	zassert_equal(found->key, target_key, "Found wrong element");
 	min_heap_remove(&my_heap, index, &removed);
+	zassert_false(min_heap_is_empty(&my_heap), "Heap should not be empty");
+	min_heap_remove(&my_heap, HEAP_CAPACITY, &removed);
+	zassert_false(min_heap_remove(&my_heap, HEAP_CAPACITY, &removed),
+		      "remove with invalid index should return false");
 	validate_heap_order_ls(&my_heap);
 	zassert_true(min_heap_is_empty(&my_heap), "Empty check fail");
 }