Add CI, code coverage and benchmarks

.gitignore

@@ -12,3 +12,5 @@
 
 # Project-local glide cache, RE: https://github.com/Masterminds/glide/issues/736
 .glide/
+
+coverage.txt

.travis.yml

@@ -0,0 +1,8 @@
+sudo: false
+language: go
+go:
+- 1.10.x
+script:
+- go test -race -coverprofile=coverage.txt -covermode=atomic -v ./...
+after_success:
+- curl -sL https://codecov.io/bash | bash

README.md

@@ -1,5 +1,10 @@
 # combos
 
+[![Build Status](https://travis-ci.org/notnil/combos.svg?branch=master)](https://travis-ci.org/notnil/combos)
+[![Go Doc](https://godoc.org/github.com/notnil/combos?status.svg)](https://godoc.org/github.com/notnil/combos)
+[![Go Report Card](https://goreportcard.com/badge/github.com/notnil/combos)](https://goreportcard.com/report/github.com/notnil/combos)
+[![codecov](https://codecov.io/gh/notnil/combos/branch/master/graph/badge.svg)](https://codecov.io/gh/notnil/combos)
+
 combos is a simple combinations package
 
 ## Usage
@@ -15,6 +20,20 @@ import (
 
 func main() {
 	fmt.Println(combos.New(7, 5))
-	// [[0 1 2 3 4] [0 1 2 3 5] [0 1 2 3 6] [0 1 2 4 5] [0 1 2 4 6] [0 1 25 6] [0 1 3 4 5] [0 1 3 4 6] [0 1 3 5 6] [0 1 4 5 6] [0 2 3 4 5] [0 2 3 4 6] [0 2 3 5 6] [0 2 4 5 6] [0 3 4 5 6] [1 2 3 4 5] [1 2 3 4 6] [1 2 3 5 6] [1 2 4 5 6] [1 3 4 5 6] [23 4 5 6]]
+	// [[0 1 2 3 4] [0 1 2 3 5] [0 1 2 3 6] [0 1 2 4 5] [0 1 2 4 6] [0 1 2 5 6] [0 1 3 4 5] [0 1 3 4 6] [0 1 3 5 6] [0 1 4 5 6] [0 2 3 4 5] [0 2 3 4 6] [0 2 3 5 6] [0 2 4 5 6] [0 3 4 5 6] [1 2 3 4 5] [1 2 3 4 6] [1 2 3 5 6] [1 2 4 5 6] [1 3 4 5 6] [2 3 4 5 6]]
 }
 ```
+
+## Benchmark
+
+```bash
+~ go test -bench=. -benchmem
+goos: darwin
+goarch: amd64
+pkg: github.com/notnil/combos
+Benchmark10C2-8     	  500000	      2628 ns/op	    4080 B/op	      62 allocs/op
+Benchmark100C2-8    	   10000	    219910 ns/op	  556416 B/op	    4980 allocs/op
+Benchmark1000C2-8   	      20	  89627977 ns/op	78746426 B/op	  499554 allocs/op
+PASS
+ok  	github.com/notnil/combos	5.582s
+```

combos_benchmark_test.go

@@ -0,0 +1,19 @@
+package combos_test
+
+import (
+	"testing"
+
+	"github.com/notnil/combos"
+)
+
+func Benchmark10C2(b *testing.B) { benchmarknCr(10, 2, b) }
+
+func Benchmark100C2(b *testing.B) { benchmarknCr(100, 2, b) }
+
+func Benchmark1000C2(b *testing.B) { benchmarknCr(1000, 2, b) }
+
+func benchmarknCr(n int, r int, b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		combos.New(n, r)
+	}
+}

combos_test.go

@@ -1,14 +1,43 @@
 package combos_test
 
 import (
+	"sort"
 	"testing"
 
 	"github.com/notnil/combos"
 )
 
-func TestCombinations(t *testing.T) {
-	results := combos.New(7, 5)
-	if len(results) != 21 {
-		t.Fatalf("expected %d results but got %d", 21, len(results))
+type combinationTest struct {
+	n        int
+	r        int
+	expected int
+}
+
+var combinationTests = []combinationTest{
+	{7, 5, 21},
+	{7, 4, 35},
+	{10, 2, 45},
+	{100, 2, 4950},
+	{1000, 2, 499500},
+}
+
+func TestCombinationsCount(t *testing.T) {
+	for _, ct := range combinationTests {
+		actual := combos.New(ct.n, ct.r)
+		if len(actual) != ct.expected {
+			t.Errorf("%dC%d: expected %d, actual %d", ct.n, ct.r, ct.expected, len(actual))
+		}
+	}
+}
+}
+
+func TestCombinationsOrdering(t *testing.T) {
+	for _, ct := range combinationTests {
+		actual := combos.New(ct.n, ct.r)
+		for _, combination := range actual {
+			if !sort.IntsAreSorted(combination) {
+				t.Errorf("%v combination is not in ascending order", combination)
+			}
+		}
 	}
 }