chore: Update assertClose in testsuite

Author: He-Pin

test_suite/stdlib.jsonnet

@@ -33,12 +33,30 @@ std.assertEqual(std.makeArray(10, function(i) i + 1), [1, 2, 3, 4, 5, 6, 7, 8, 9
 std.assertEqual(std.makeArray(0, function(i) null), []) &&
 
 local assertClose(a, b) =
+  // Using 1e-12 as tolerance. Jsonnet uses double-precision floats with machine epsilon of 2**-53 ≈ 1.11e-16.
+  // This tolerance is ~9000x the machine epsilon, which is quite lenient and should work across
+  // different platforms and math libraries.
+  //
+  // We use a combination of absolute and relative error to handle both small and large values:
+  // - For values near zero, we use absolute error to avoid division issues
+  // - For larger values, we use relative error to maintain precision
+  //
+  // This correctly handles cases like:
+  //   assertClose(1e-15, 0) - should pass (both are essentially zero)
+  //   assertClose(-100, 0) - should fail (significant difference)
+  //   assertClose(std.sin(std.pi), 0) - should pass (tiny floating point error)
+  local abs_a = std.abs(a);
+  local abs_b = std.abs(b);
+  local diff = std.abs(a - b);
+  local max_abs = std.max(abs_a, abs_b);
   local err =
-    if b == 0 then
-      a - b
+    if abs_a == 0 && abs_b == 0 then
+      0  // Both are exactly zero, so no error
+    else if max_abs < 1e-12 then
+      diff  // For very small values, use absolute error
     else
-      if a / b - 1 > 0 then a / b - 1 else 1 - a / b;
-  if err > 0.000005 then
+      diff / max_abs;  // For larger values, use relative error
+  if err > 1e-12 then
     error 'Assertion failed (error ' + err + '). ' + a + ' !~ ' + b
   else
     true;