diff --git a/.travis.yml b/.travis.yml
index a7efa7b..ff6379e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,19 +1,40 @@
+os:
+  - linux
+  - osx
+  - windows
+
 language: go
 
 sudo: required
 
 go:
+  # "1.x" always refers to the latest Go version, inc. the patch release.
+  # e.g. "1.x" is 1.13 until 1.13.1 is available.
+  - 1.x
   - 1.6.x
   - 1.7.x
+  - 1.8.x
+  - 1.9.x
+  - 1.10.x
+  - 1.11.x
+  - 1.12.x
+  - 1.13.x
+  - 1.14.x
   - tip
 
-env:
-    - GIMME_OS=linux GIMME_ARCH=amd64
-    - GIMME_OS=darwin GIMME_ARCH=amd64
-    - GIMME_OS=windows GIMME_ARCH=amd64
+matrix:
+  allow_failures:
+    - os: windows
+      go: tip
+  exclude:
+      # OSX 1.6.4 is not present in travis.
+      # https://github.com/travis-ci/travis-ci/issues/10309
+    - go: 1.6.x
+      os: osx
 
 install:
-    - go get -d -v ./...
+  - go get -d -v ./...
 
 script:
-    - go build -v ./...
+  - go build -v ./...
+  - go test ./...
diff --git a/README.md b/README.md
index eb2a72f..7034a96 100644
--- a/README.md
+++ b/README.md
@@ -31,8 +31,12 @@ func Test(t *testing.T) {
 
 ## Color
 
-To turn off the colors, run `go test` with the `-nocolor` flag.
+To turn off the colors, run `go test` with the `-nocolor` flag, or with the env var `IS_NO_COLOR=true`.
 
 ```
 go test -nocolor
 ```
+
+```
+IS_NO_COLOR=true go test
+```
diff --git a/is-1.7.go b/is-1.7.go
new file mode 100644
index 0000000..c19f23f
--- /dev/null
+++ b/is-1.7.go
@@ -0,0 +1,64 @@
+// +build go1.7
+
+package is
+
+import (
+	"regexp"
+	"runtime"
+)
+
+// Helper marks the calling function as a test helper function.
+// When printing file and line information, that function will be skipped.
+//
+// Available with Go 1.7 and later.
+func (is *I) Helper() {
+	is.helpers[callerName(1)] = struct{}{}
+}
+
+// callerName gives the function name (qualified with a package path)
+// for the caller after skip frames (where 0 means the current function).
+func callerName(skip int) string {
+	// Make room for the skip PC.
+	var pc [1]uintptr
+	n := runtime.Callers(skip+2, pc[:]) // skip + runtime.Callers + callerName
+	if n == 0 {
+		panic("is: zero callers found")
+	}
+	frames := runtime.CallersFrames(pc[:n])
+	frame, _ := frames.Next()
+	return frame.Function
+}
+
+// The maximum number of stack frames to go through when skipping helper functions for
+// the purpose of decorating log messages.
+const maxStackLen = 50
+
+var reIsSourceFile = regexp.MustCompile("is(-1.7)?\\.go$")
+
+func (is *I) callerinfo() (path string, line int, ok bool) {
+	var pc [maxStackLen]uintptr
+	// Skip two extra frames to account for this function
+	// and runtime.Callers itself.
+	n := runtime.Callers(2, pc[:])
+	if n == 0 {
+		panic("is: zero callers found")
+	}
+	frames := runtime.CallersFrames(pc[:n])
+	var firstFrame, frame runtime.Frame
+	for more := true; more; {
+		frame, more = frames.Next()
+		if reIsSourceFile.MatchString(frame.File) {
+			continue
+		}
+		if firstFrame.PC == 0 {
+			firstFrame = frame
+		}
+		if _, ok := is.helpers[frame.Function]; ok {
+			// Frame is inside a helper function.
+			continue
+		}
+		return frame.File, frame.Line, true
+	}
+	// If no "non-helper" frame is found, the first non is frame is returned.
+	return firstFrame.File, firstFrame.Line, true
+}
diff --git a/is-1.7_test.go b/is-1.7_test.go
new file mode 100644
index 0000000..f4249c7
--- /dev/null
+++ b/is-1.7_test.go
@@ -0,0 +1,53 @@
+// +build go1.7
+
+package is
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+)
+
+// TestSubtests ensures subtests work as expected.
+// https://github.com/matryer/is/issues/1
+func TestSubtests(t *testing.T) {
+	t.Run("sub1", func(t *testing.T) {
+		is := New(t)
+		is.Equal(1+1, 2)
+	})
+}
+
+func TestHelper(t *testing.T) {
+	tests := []struct {
+		name             string
+		helper           bool
+		expectedFilename string
+	}{
+		{
+			name:             "without helper",
+			helper:           false,
+			expectedFilename: "is_helper_test.go",
+		},
+		{
+			name:             "with helper",
+			helper:           true,
+			expectedFilename: "is-1.7_test.go",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			tt := &mockT{}
+			is := NewRelaxed(tt)
+
+			var buf bytes.Buffer
+			is.out = &buf
+			helper(is, tc.helper)
+			actual := buf.String()
+			t.Log(actual)
+			if !strings.Contains(actual, tc.expectedFilename) {
+				t.Errorf("string does not contain correct filename: %s", actual)
+			}
+		})
+	}
+}
diff --git a/is-before-1.7.go b/is-before-1.7.go
new file mode 100644
index 0000000..c62f872
--- /dev/null
+++ b/is-before-1.7.go
@@ -0,0 +1,23 @@
+// +build !go1.7
+
+package is
+
+import (
+	"regexp"
+	"runtime"
+)
+
+var reIsSourceFile = regexp.MustCompile("is(-before-1.7)?\\.go$")
+
+func (is *I) callerinfo() (path string, line int, ok bool) {
+	for i := 0; ; i++ {
+		_, path, line, ok = runtime.Caller(i)
+		if !ok {
+			return
+		}
+		if reIsSourceFile.MatchString(path) {
+			continue
+		}
+		return path, line, true
+	}
+}
diff --git a/is.go b/is.go
index 74a6073..c363c82 100644
--- a/is.go
+++ b/is.go
@@ -45,7 +45,6 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
-	"runtime"
 	"strings"
 	"testing"
 )
@@ -69,12 +68,15 @@ type I struct {
 	fail     func()
 	out      io.Writer
 	colorful bool
+
+	helpers map[string]struct{} // functions to be skipped when writing file/line info
 }
 
 var noColorFlag bool
 
 func init() {
-	flag.BoolVar(&noColorFlag, "nocolor", false, "turns off colors")
+	envNoColor := os.Getenv("IS_NO_COLOR") == "true"
+	flag.BoolVar(&noColorFlag, "nocolor", envNoColor, "turns off colors")
 }
 
 // New makes a new testing helper using the specified
@@ -82,7 +84,7 @@ func init() {
 // In strict mode, failures call T.FailNow causing the test
 // to be aborted. See NewRelaxed for alternative behavior.
 func New(t T) *I {
-	return &I{t, t.FailNow, os.Stdout, !noColorFlag}
+	return &I{t, t.FailNow, os.Stdout, !noColorFlag, map[string]struct{}{}}
 }
 
 // NewRelaxed makes a new testing helper using the specified
@@ -90,7 +92,7 @@ func New(t T) *I {
 // In relaxed mode, failures call T.Fail allowing
 // multiple failures per test.
 func NewRelaxed(t T) *I {
-	return &I{t, t.Fail, os.Stdout, !noColorFlag}
+	return &I{t, t.Fail, os.Stdout, !noColorFlag, map[string]struct{}{}}
 }
 
 func (is *I) log(args ...interface{}) {
@@ -146,23 +148,14 @@ func (is *I) True(expression bool) {
 //
 //	your_test.go:123: Hey Mat != Hi Mat // greeting
 func (is *I) Equal(a, b interface{}) {
-	if !areEqual(a, b) {
-		if isNil(a) || isNil(b) {
-			aLabel := is.valWithType(a)
-			bLabel := is.valWithType(b)
-			if isNil(a) {
-				aLabel = "<nil>"
-			}
-			if isNil(b) {
-				bLabel = "<nil>"
-			}
-			is.logf("%s != %s", aLabel, bLabel)
-			return
-		}
-		if reflect.ValueOf(a).Type() == reflect.ValueOf(b).Type() {
-			is.logf("%v != %v", a, b)
-			return
-		}
+	if areEqual(a, b) {
+		return
+	}
+	if isNil(a) || isNil(b) {
+		is.logf("%s != %s", is.valWithType(a), is.valWithType(b))
+	} else if reflect.ValueOf(a).Type() == reflect.ValueOf(b).Type() {
+		is.logf("%v != %v", a, b)
+	} else {
 		is.logf("%s != %s", is.valWithType(a), is.valWithType(b))
 	}
 }
@@ -198,6 +191,9 @@ func (is *I) NewRelaxed(t *testing.T) *I {
 }
 
 func (is *I) valWithType(v interface{}) string {
+	if isNil(v) {
+		return "<nil>"
+	}
 	if is.colorful {
 		return fmt.Sprintf("%[1]s%[3]T(%[2]s%[3]v%[1]s)%[2]s", colorType, colorNormal, v)
 	}
@@ -237,15 +233,12 @@ func isNil(object interface{}) bool {
 
 // areEqual gets whether a equals b or not.
 func areEqual(a, b interface{}) bool {
-	if isNil(a) || isNil(b) {
-		if isNil(a) && !isNil(b) {
-			return false
-		}
-		if !isNil(a) && isNil(b) {
-			return false
-		}
+	if isNil(a) && isNil(b) {
 		return true
 	}
+	if isNil(a) || isNil(b) {
+		return false
+	}
 	if reflect.DeepEqual(a, b) {
 		return true
 	}
@@ -254,19 +247,6 @@ func areEqual(a, b interface{}) bool {
 	return aValue == bValue
 }
 
-func callerinfo() (path string, line int, ok bool) {
-	for i := 0; ; i++ {
-		_, path, line, ok = runtime.Caller(i)
-		if !ok {
-			return
-		}
-		if strings.HasSuffix(path, "is.go") {
-			continue
-		}
-		return path, line, true
-	}
-}
-
 // loadComment gets the Go comment from the specified line
 // in the specified file.
 func loadComment(path string, line int) (string, bool) {
@@ -280,7 +260,7 @@ func loadComment(path string, line int) (string, bool) {
 	for s.Scan() {
 		if i == line {
 			text := s.Text()
-			commentI := strings.Index(text, "//")
+			commentI := strings.Index(text, "// ")
 			if commentI == -1 {
 				return "", false // no comment
 			}
@@ -339,7 +319,7 @@ func loadArguments(path string, line int) (string, bool) {
 // and inserts the final newline if needed and indentation tabs for formatting.
 // this function was copied from the testing framework and modified.
 func (is *I) decorate(s string) string {
-	path, lineNumber, ok := callerinfo() // decorate + log + public function.
+	path, lineNumber, ok := is.callerinfo() // decorate + log + public function.
 	file := filepath.Base(path)
 	if ok {
 		// Truncate file name at last file name separator.
@@ -362,6 +342,9 @@ func (is *I) decorate(s string) string {
 	if is.colorful {
 		buf.WriteString(colorNormal)
 	}
+
+	s = escapeFormatString(s)
+
 	lines := strings.Split(s, "\n")
 	if l := len(lines); l > 1 && lines[l-1] == "" {
 		lines = lines[:l-1]
@@ -384,6 +367,7 @@ func (is *I) decorate(s string) string {
 			buf.WriteString(colorComment)
 		}
 		buf.WriteString(" // ")
+		comment = escapeFormatString(comment)
 		buf.WriteString(comment)
 		if is.colorful {
 			buf.WriteString(colorNormal)
@@ -393,9 +377,14 @@ func (is *I) decorate(s string) string {
 	return buf.String()
 }
 
+// escapeFormatString escapes strings for use in formatted functions like Sprintf.
+func escapeFormatString(fmt string) string {
+	return strings.Replace(fmt, "%", "%%", -1)
+}
+
 const (
 	colorNormal  = "\u001b[39m"
-	colorComment = "\u001b[32m"
+	colorComment = "\u001b[31m"
 	colorFile    = "\u001b[90m"
 	colorType    = "\u001b[90m"
 )
diff --git a/is_helper_test.go b/is_helper_test.go
new file mode 100644
index 0000000..6bcbf77
--- /dev/null
+++ b/is_helper_test.go
@@ -0,0 +1,10 @@
+// +build go1.7
+
+package is
+
+func helper(is *I, helper bool) {
+	if helper {
+		is.Helper()
+	}
+	is.True(false)
+}
diff --git a/is_test.go b/is_test.go
index b27dcf2..7cb48a7 100644
--- a/is_test.go
+++ b/is_test.go
@@ -140,6 +140,15 @@ var tests = []struct {
 		},
 		Fail: ``,
 	},
+	{
+		N: `Equal("20% VAT", "0.2 VAT")`,
+		F: func(is *I) {
+			s1 := "20% VAT"
+			s2 := "0.2 VAT"
+			is.Equal(s1, s2) // strings
+		},
+		Fail: ` // strings`,
+	},
 
 	// Fail
 	{
@@ -268,11 +277,16 @@ func TestLoadArguments(t *testing.T) {
 	}
 }
 
-// TestSubtests ensures subtests work as expected.
-// https://github.com/matryer/is/issues/1
-func TestSubtests(t *testing.T) {
-	t.Run("sub1", func(t *testing.T) {
-		is := New(t)
-		is.Equal(1+1, 2)
-	})
+// TestArgumentsEscape ensures strings are correctly escaped before printing.
+// https://github.com/matryer/is/issues/27
+func TestFormatStringEscape(t *testing.T) {
+	tt := &mockT{}
+	is := NewRelaxed(tt)
+	var buf bytes.Buffer
+	is.out = &buf
+	is.Equal("20% VAT", "0.2 VAT") // % symbol should be correctly printed
+	actual := buf.String()
+	if strings.Contains(actual, `%!`) {
+		t.Errorf("string was not escaped correctly: %s", actual)
+	}
 }
diff --git a/misc/delicious-failures.png b/misc/delicious-failures.png
index b1e0d01..676d893 100644
Binary files a/misc/delicious-failures.png and b/misc/delicious-failures.png differ