Enhance docs, add more tests in AffineConverter (#5915)

src/test/java/com/thealgorithms/conversions/AffineConverterTest.java

@@ -16,31 +16,39 @@ public class AffineConverterTest {
     }
 
     @Test
-    void testConstructor() {
+    void testConstructorWithValidValues() {
         assertEquals(3.0, converter.convert(0.0), "Expected value when input is 0.0");
         assertEquals(5.0, converter.convert(1.0), "Expected value when input is 1.0");
-        assertEquals(7.0, converter.convert(2.0), "Expected value when input is 2.0");
     }
 
     @Test
-    void testConvert() {
-        assertEquals(3.0, converter.convert(0.0), "Conversion at 0.0 should equal the intercept");
-        assertEquals(7.0, converter.convert(2.0), "2.0 should convert to 7.0");
-        assertEquals(11.0, converter.convert(4.0), "4.0 should convert to 11.0");
+    void testConstructorWithInvalidValues() {
+        assertThrows(IllegalArgumentException.class, () -> new AffineConverter(Double.NaN, 3.0), "Constructor should throw IllegalArgumentException for NaN slope");
+    }
+
+    @Test
+    void testConvertWithNegativeValues() {
+        assertEquals(-1.0, converter.convert(-2.0), "Negative input should convert correctly");
+        assertEquals(-3.0, new AffineConverter(-1.0, -1.0).convert(2.0), "Slope and intercept can be negative");
+    }
+
+    @Test
+    void testConvertWithFloatingPointPrecision() {
+        double result = new AffineConverter(1.3333, 0.6667).convert(3.0);
+        assertEquals(4.6666, result, 1e-4, "Conversion should maintain floating-point precision");
     }
 
     @Test
     void testInvert() {
         AffineConverter inverted = converter.invert();
-        assertEquals(0.0, inverted.convert(3.0), "Inverted converter should return 0.0 for input 3.0");
-        assertEquals(1.0, inverted.convert(5.0), "Inverted converter should return 1.0 for input 5.0");
-        assertEquals(2.0, inverted.convert(7.0), "Inverted converter should return 2.0 for input 7.0");
+        assertEquals(0.0, inverted.convert(3.0), "Inverted should return 0.0 for input 3.0");
+        assertEquals(1.0, inverted.convert(5.0), "Inverted should return 1.0 for input 5.0");
     }
 
     @Test
     void testInvertWithZeroSlope() {
         AffineConverter zeroSlopeConverter = new AffineConverter(0.0, 3.0);
-        assertThrows(AssertionError.class, zeroSlopeConverter::invert, "Invert should throw assertion error when slope is zero");
+        assertThrows(AssertionError.class, zeroSlopeConverter::invert, "Invert should throw AssertionError when slope is zero");
     }
 
     @Test
@@ -50,6 +58,30 @@ public class AffineConverterTest {
 
         assertEquals(7.0, composed.convert(0.0), "Expected composed conversion at 0.0");
         assertEquals(9.0, composed.convert(1.0), "Expected composed conversion at 1.0");
-        assertEquals(11.0, composed.convert(2.0), "Expected composed conversion at 2.0");
+    }
+
+    @Test
+    void testMultipleCompositions() {
+        AffineConverter c1 = new AffineConverter(2.0, 1.0);
+        AffineConverter c2 = new AffineConverter(3.0, -2.0);
+        AffineConverter c3 = c1.compose(c2); // (2x + 1) ∘ (3x - 2) => 6x - 1
+
+        assertEquals(-3.0, c3.convert(0.0), "Composed transformation should return -3.0 at 0.0");
+        assertEquals(3.0, c3.convert(1.0), "Composed transformation should return 3.0 at 1.0");
+    }
+
+    @Test
+    void testIdentityComposition() {
+        AffineConverter identity = new AffineConverter(1.0, 0.0);
+        AffineConverter composed = converter.compose(identity);
+
+        assertEquals(3.0, composed.convert(0.0), "Identity composition should not change the transformation");
+        assertEquals(7.0, composed.convert(2.0), "Identity composition should behave like the original");
+    }
+
+    @Test
+    void testLargeInputs() {
+        double largeValue = 1e6;
+        assertEquals(2.0 * largeValue + 3.0, converter.convert(largeValue), "Should handle large input values without overflow");
     }
 }