Fix voltage_within voltage attr check

checks.zen

@@ -12,14 +12,12 @@ def voltage_within(
         # drop nominal in within:
         within = VoltageRange(min=within.min, max=within.max)
         # ensure voltage is within within
-        min_valid = voltage.min >= within.min
-        max_valid = voltage.max <= within.max
         err_msg = "Voltage range " + str(voltage) + " of " + net_name + " is not within " + str(within)
-        check(min_valid and max_valid, err_msg)
+        check(voltage in within, err_msg)
 
     def check_gen(power: Power, severity: Severity = severity, name: str = name):
         check_name = power.NET.name + "_" + name
-        if not power.voltage:
+        if not hasattr(power, "voltage"):
             return
         builtin.add_electrical_check(
             name=check_name,

test/test_checks.zen

@@ -0,0 +1,24 @@
+load("../checks.zen", "voltage_within")
+load("../interfaces.zen", "Power", "VoltageRange")
+
+# Test 3.3V rail with tolerance
+v3v3 = Power("3V3", voltage=VoltageRange("3.3V 1%"))
+# Check if 3.3V +/- 1% is within 3.3V +/- 5%
+check_3v3 = voltage_within("3.3V 5%")
+check_3v3(v3v3)
+
+# Test 5V rail with explicit range
+v5 = Power("5V", voltage=VoltageRange("5V"))
+# Check if 5V is within 4.5V to 5.5V (using +/- 10% notation)
+check_5v = voltage_within("5V 10%")
+check_5v(v5)
+
+# Test with tighter tolerance on the rail than the check
+v1v8 = Power("1V8", voltage=VoltageRange("1.8V 1%"))
+check_1v8 = voltage_within("1.8V 5%")
+check_1v8(v1v8)
+
+# Test rail with no voltage set (should be ignored)
+v_unknown = Power("UNKNOWN")
+check_unknown = voltage_within("5V 10%")
+check_unknown(v_unknown)