Challenge copilot-workshops#1, add tests for subtraction

Author: fred-meng

test/arithmetic.test.js

@@ -94,8 +94,58 @@ describe('Arithmetic', function () {
     });
 
 // TODO: Challenge #1
- 
-
+// add tests for subtraction
+    describe('Subtraction', function () {
+        it('subtracts two positive integers', function (done) {
+            request.get('/arithmetic?operation=subtract&operand1=21&operand2=18')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 3 });
+                    done();
+                });
+        });
+        it('subtracts a positive integer from zero', function (done) {
+            request.get('/arithmetic?operation=subtract&operand1=0&operand2=21')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: -21 });
+                    done();
+                });
+        });
+        it('subtracts a negative integer from a positive integer', function (done) {
+            request.get('/arithmetic?operation=subtract&operand1=21&operand2=-42')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 63 });
+                    done();
+                });
+        });
+        it('subtracts two negative integers', function (done) {
+            request.get('/arithmetic?operation=subtract&operand1=-21&operand2=-21')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 0 });
+                    done();
+                });
+        });
+        it('subtracts a floating point number from an integer', function (done) {
+            request.get('/arithmetic?operation=subtract&operand1=2.5&operand2=1.5')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 1 });
+                    done();
+                });
+        });
+        it('subtracts with negative exponent', function (done) {
+            request.get('/arithmetic?operation=subtract&operand1=1.2e-5&operand2=-1.2e-5')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 2.4e-5 });
+                    done();
+                });
+        });
+    });
+    
     describe('Multiplication', function () {
         it('multiplies two positive integers', function (done) {
             request.get('/arithmetic?operation=multiply&operand1=21&operand2=2')