Initial commit of modash

This was taken from github.com/lmika/gopkgs/fp

moslice/filter_test.go

@@ -0,0 +1,29 @@
+package moslice_test
+
+import (
+	"lmika.dev/pkg/modash/moslice"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFilter(t *testing.T) {
+	var (
+		ints = []int{1, 2, 3, 4, 5}
+		strs = []string{"foo", "bar", "baz"}
+	)
+
+	t.Run("should filter items matching the predicate", func(t *testing.T) {
+		assert.Equal(t, []int{2, 4}, moslice.Filter(ints, func(x int) bool { return x%2 == 0 }))
+		assert.Equal(t, []string{"bar", "baz"}, moslice.Filter(strs, func(x string) bool { return strings.Contains(x, "b") }))
+	})
+
+	t.Run("should moslice nil if the passed in slice is nil", func(t *testing.T) {
+		assert.Nil(t, moslice.Filter(nil, func(x int) bool { return x%2 == 0 }))
+	})
+
+	t.Run("should return empty slice if the passed in slice is empty slice", func(t *testing.T) {
+		assert.Equal(t, []int{}, moslice.Filter([]int{}, func(x int) bool { return x%2 == 0 }))
+	})
+}