Add tests for coins

types/coin.go

@@ -72,10 +72,7 @@ func (coins Coins) IsValid() bool {
 	}
 }
 
-// Plus combines to sets of coins
-//
-// TODO: handle empty coins!
-// Currently appends an empty coin ...
+// Plus combines two sets of coins
 func (coins Coins) Plus(coinsB Coins) Coins {
 	sum := []Coin{}
 	indexA, indexB := 0, 0
@@ -110,7 +107,6 @@ func (coins Coins) Plus(coinsB Coins) Coins {
 			indexB++
 		}
 	}
-	return sum
 }
 
 // Negative returns a set of coins with all amount negative

types/coin_test.go

@@ -52,7 +52,28 @@ func TestCoins(t *testing.T) {
 
 }
 
-//Test the parse coin and parse coins functionality
+func TestPlusCoins(t *testing.T) {
+	assert := assert.New(t)
+
+	cases := []struct {
+		inputOne Coins
+		inputTwo Coins
+		expected Coins
+	}{
+		{Coins{{"A", 1}, {"B", 1}}, Coins{{"A", 1}, {"B", 1}}, Coins{{"A", 2}, {"B", 2}}},
+		{Coins{{"A", 0}, {"B", 1}}, Coins{{"A", 0}, {"B", 0}}, Coins{{"B", 1}}},
+		{Coins{{"A", 0}, {"B", 0}}, Coins{{"A", 0}, {"B", 0}}, Coins{}},
+		{Coins{{"A", 1}, {"B", 0}}, Coins{{"A", -1}, {"B", 0}}, Coins{}},
+	}
+
+	for _, tc := range cases {
+		res := tc.inputOne.Plus(tc.inputTwo)
+		assert.True(res.IsValid())
+		assert.Equal(res, tc.expected)
+	}
+}
+
+//Test the parsing of Coin and Coins
 func TestParse(t *testing.T) {
 
 	cases := []struct {