List check utils.

utils/list.go

@@ -0,0 +1,23 @@
+package utils
+
+import (
+	"fmt"
+)
+
+// StringsIsSubset checks that subset is strict subset of full, and returns
+// error formatted with errorFmt otherwise
+func StringsIsSubset(subset []string, full []string, errorFmt string) error {
+	for checked := range subset {
+		found := false
+		for s := range full {
+			if checked == s {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return fmt.Errorf(errorFmt, checked, full)
+		}
+	}
+	return nil
+}

utils/list_test.go

@@ -0,0 +1,16 @@
+package utils
+
+import (
+	. "launchpad.net/gocheck"
+)
+
+type ListSuite struct {
+}
+
+func (s *ListSuite) TestStringsIsSubset(c *C) {
+	err := StringsIsSubset([]string{"a", "b"}, []string{"a", "b", "c"}, "[%s]")
+	c.Assert(err, IsNil)
+
+	err = StringsIsSubset([]string{"b", "a"}, []string{"b", "c"}, "[%s]")
+	c.Assert(err, ErrorMatches, "[a]")
+}