Ensure scale >= 0 in conversion results

Author: fkleedorfer

CHANGELOG.md

@@ -9,7 +9,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
-- `Unit.convert()` and `Unit.getConversionMultiplier(Unit)` now strip any trailing fractional zeros.
+- `Unit.convert()` and `Unit.getConversionMultiplier(Unit)` now strip any trailing fractional zeros and the 
+  scale of the result is >= 0.
 
 ## [7.0.0] - 2025-07-22
 

qudtlib-model/src/main/java/io/github/qudtlib/model/Unit.java

@@ -401,11 +401,16 @@ public BigDecimal convert(BigDecimal value, Unit toUnit, QuantityKind quantityKi
                         ? BigDecimal.ZERO
                         : toUnit.getConversionOffset().orElse(BigDecimal.ZERO);
         BigDecimal toMultiplier = toUnit.getConversionMultiplier().orElse(BigDecimal.ONE);
-        return value.add(fromOffset)
-                .multiply(fromMultiplier, MathContext.DECIMAL128)
-                .divide(toMultiplier, MathContext.DECIMAL128)
-                .subtract(toOffset)
-                .stripTrailingZeros();
+        BigDecimal result =
+                value.add(fromOffset)
+                        .multiply(fromMultiplier, MathContext.DECIMAL128)
+                        .divide(toMultiplier, MathContext.DECIMAL128)
+                        .subtract(toOffset)
+                        .stripTrailingZeros();
+        if (result.scale() < 0) {
+            result = result.setScale(0);
+        }
+        return result;
     }
 
     /**
@@ -448,7 +453,11 @@ public BigDecimal getConversionMultiplier(Unit toUnit) {
                                                         toUnit.getConversionMultiplier().isEmpty()
                                                                 ? "no multiplier"
                                                                 : "has multiplier")));
-        return result.stripTrailingZeros();
+        result = result.stripTrailingZeros();
+        if (result.scale() < 0) {
+            result = result.setScale(0);
+        }
+        return result;
     }
 
     public boolean conversionOffsetDiffers(Unit other) {

qudtlib-test/src/test/java/io/github/qudtlib/QudtTests.java

@@ -569,10 +569,12 @@ public void testMilliSV__PER__HR_to_MicroSV__PER__HR() {
                                                 u.getIriLocalname(),
                                                 u.getConversionMultiplier().get().toString())));
          */
-        MatcherAssert.assertThat(
-                Qudt.convert(
-                        new BigDecimal("15.12"), Units.MilliSV__PER__HR, Units.MicroSV__PER__HR),
-                Matchers.comparesEqualTo(new BigDecimal(15120)));
+        BigDecimal converted = Qudt.convert(
+                        new BigDecimal("15.12"), Units.MilliSV__PER__HR, Units.MicroSV__PER__HR);
+        MatcherAssert.assertThat(converted,Matchers.comparesEqualTo(new BigDecimal(15120)));
+        BigDecimal expected = new BigDecimal(15120);
+        assertEquals(expected, converted) ;
+
     }
 
     @Test