pbio/math: Document and test square root.

Author: laurensvalk

lib/pbio/src/math.c

@@ -116,6 +116,14 @@ int32_t pbio_math_clamp(int32_t value, int32_t abs_max) {
     return pbio_math_bind(value, -abs_max, abs_max);
 }
 
+/**
+ * Gets the square root.
+ *
+ * If @p n <= 0, it returns 0.
+ *
+ * @param [in]  n       The input value
+ * @return              The square root.
+ */
 int32_t pbio_math_sqrt(int32_t n) {
     if (n <= 0) {
         return 0;

lib/pbio/test/src/math.c

@@ -19,12 +19,19 @@ static void test_clamp(void *env) {
 }
 
 static void test_sqrt(void *env) {
-    tt_want(pbio_math_sqrt(0) == 0);
-    tt_want(pbio_math_sqrt(1) == 1);
-    tt_want(pbio_math_sqrt(4) == 2);
-    tt_want(pbio_math_sqrt(400) == 20);
-    tt_want(pbio_math_sqrt(40000) == 200);
-    tt_want(pbio_math_sqrt(400000000) == 20000);
+    tt_want_int_op(pbio_math_sqrt(0), ==, 0);
+    tt_want_int_op(pbio_math_sqrt(1), ==, 1);
+    tt_want_int_op(pbio_math_sqrt(4), ==, 2);
+    tt_want_int_op(pbio_math_sqrt(400), ==, 20);
+    tt_want_int_op(pbio_math_sqrt(40000), ==, 200);
+    tt_want_int_op(pbio_math_sqrt(400000000), ==, 20000);
+
+    // Negative square roots do not exist but are expected to return 0.
+    tt_want_int_op(pbio_math_sqrt(-36), ==, 0);
+
+    for (int32_t s = 0; s < INT32_MAX - 255; s += 256) {
+        tt_want_int_op(pbio_math_sqrt(s), ==, sqrt(s));
+    }
 }
 
 static void test_atan2(void *env) {