1 files changed, 31 insertions, 3 deletions

diff --git a/Week7/test/polynomial/PolynomialTest.java b/Week7/test/polynomial/PolynomialTest.java
index 13f7405..c0f9c4b 100644
--- a/Week7/test/polynomial/PolynomialTest.java
+++ b/Week7/test/polynomial/PolynomialTest.java
@@ -43,8 +43,10 @@ public class PolynomialTest {
     @Test
     public void testToString() {
         System.out.println("toString");
-        // Test exp=0, exp=1, exp>1, positive & negative integer & floating point coefficients
+        // Test exp=0, exp=1, exp>1, positive & negative integer & floating point coefficients all at once
         assertEquals("3.000000x^5-4.000000x+2.500000-3.400000x^-7", new Polynomial("3 5 -4 1 2.5 0 -3.4 -7").toString());
+        // Test zero polynomial
+        assertEquals("", new Polynomial().toString());
     }
 
     /**
@@ -53,6 +55,7 @@ public class PolynomialTest {
     @Test
     public void testMinus() {
         System.out.println("minus");
+        // Test cancelling out and exponents that don't exist in either of the two polynomials all at once
         Polynomial instance = new Polynomial("7 4 -4 2 3 1 5 0");       // 7x^4 - 4x^2 + 3x + 5
         instance.minus(new Polynomial("5 3 4 2 3 1 10 0"));             // 5x^3 + 4x^2 + 3x + 10
         assertEquals(new Polynomial("7 4 -5 3 -8 2 -5 0"), instance);   // 7x^4 - 5x^3 - 8x^2 - 5
@@ -64,9 +67,21 @@ public class PolynomialTest {
     @Test
     public void testTimes() {
         System.out.println("times");
+        
+        // Simple case
         Polynomial instance = new Polynomial("7 1 6 3");
         instance.times(new Polynomial("5 3 4 2"));
         assertEquals(new Polynomial("30 6 24 5 35 4 28 3"), instance);
+        
+        // Simple case with zero polynomial
+        instance = new Polynomial("5 3");
+        instance.times(new Polynomial());
+        assertEquals(new Polynomial(), instance);
+        
+        // Advanced case with coefficient 0 in the result
+        instance = new Polynomial("4 4 2 3");                           // 4x^4 + 2x^3
+        instance.times(new Polynomial("2 2 -4 3"));                     // 2x^2 - 4x^3
+        assertEquals(new Polynomial("4 5 -16 7"), instance);            // 4x^5 - 16x^7 (exponent 6 cancels out)
     }
 
     /**
@@ -88,7 +103,18 @@ public class PolynomialTest {
     @Test
     public void testEquals() {
         System.out.println("equals");
+        // Order of terms irrelevant
         assertEquals(true, new Polynomial("4 2 3 5").equals(new Polynomial("3 5 4 2")));
+        // Terms with same exponent are added
+        assertEquals(true, new Polynomial("5 5 10 5").equals(new Polynomial("15 5")));
+        // Simple coefficient 0 removed
+        assertEquals(true, new Polynomial("0 7").equals(new Polynomial()));
+        // Advanced coefficient 0 removed
+        assertEquals(true, new Polynomial("5 10 -5 10").equals(new Polynomial()));
+        // Difference in exponent matters
+        assertEquals(false, new Polynomial("10 0").equals(new Polynomial("10 1")));
+        // Difference in coefficient matters
+        assertEquals(false, new Polynomial("10 0").equals(new Polynomial("5 0")));
     }
 
     /**
@@ -97,6 +123,7 @@ public class PolynomialTest {
     @Test
     public void testPlus_Polynomial() {
         System.out.println("plus");
+        // Test cancelling out and exponents that don't exist in either of the two polynomials all at once
         Polynomial instance = new Polynomial("7 4 -4 2 7 1 5 0");       // 7x^4 - 4x^2 + 7x + 5
         instance.plus(new Polynomial("5 3 4 2 3 1 10 0"));              // 5x^3 + 4x^2 + 3x + 10
         assertEquals(new Polynomial("7 4 5 3 10 1 15 0"), instance);    // 7x^4 + 5x^3 + 10x + 15
@@ -108,8 +135,9 @@ public class PolynomialTest {
     @Test
     public void testApply() {
         System.out.println("apply");
-        Polynomial instance = new Polynomial("5 4 0.5 3 9 2 8 0");
-        assertEquals(422670.5, instance.apply(17.0), 0.0);
+        // Test zero coefficient, floating point coefficient and negative coefficient all at once
+        Polynomial instance = new Polynomial("0 7 5 4 0.5 3 9 2 -8 0");
+        assertEquals(422654.5, instance.apply(17.0), 0.0);
     }
     
 }