diff --git a/README.md b/README.md
index 26781bb..ee435ad 100644
--- a/README.md
+++ b/README.md
@@ -38,6 +38,14 @@ You can also call the test helper at runtime if needed:
         TestHelper(&testing.RuntimeT{})
     }
 
+## Versioning
+
+The tagged version matches the version of Go that the interface is
+compatible with. For example, the version "1.14.0" is for Go 1.14 and
+introduced the `Cleanup` function. The patch version (the ".0" in the
+prior example) is used to fix any bugs found in this library and has no
+correlation to the supported Go version.
+
 ## Why?!
 
 **Why would I call a test helper that takes a *testing.T at runtime?**
diff --git a/go.mod b/go.mod
index 062796d..acc65c4 100644
--- a/go.mod
+++ b/go.mod
@@ -1 +1,3 @@
 module github.com/mitchellh/go-testing-interface
+
+go 1.14
diff --git a/testing.go b/testing.go
index 204afb4..f709093 100644
--- a/testing.go
+++ b/testing.go
@@ -1,5 +1,3 @@
-// +build !go1.9
-
 package testing
 
 import (
@@ -12,6 +10,7 @@ import (
 // In unit tests you can just pass a *testing.T struct. At runtime, outside
 // of tests, you can pass in a RuntimeT struct from this package.
 type T interface {
+	Cleanup(func())
 	Error(args ...interface{})
 	Errorf(format string, args ...interface{})
 	Fail()
@@ -19,6 +18,7 @@ type T interface {
 	Failed() bool
 	Fatal(args ...interface{})
 	Fatalf(format string, args ...interface{})
+	Helper()
 	Log(args ...interface{})
 	Logf(format string, args ...interface{})
 	Name() string
@@ -31,10 +31,13 @@ type T interface {
 // RuntimeT implements T and can be instantiated and run at runtime to
 // mimic *testing.T behavior. Unlike *testing.T, this will simply panic
 // for calls to Fatal. For calls to Error, you'll have to check the errors
-// list to determine whether to exit yourself. Name and Skip methods are
-// unimplemented noops.
+// list to determine whether to exit yourself.
+//
+// Cleanup does NOT work, so if you're using a helper that uses Cleanup,
+// there may be dangling resources.
 type RuntimeT struct {
-	failed bool
+	skipped bool
+	failed  bool
 }
 
 func (t *RuntimeT) Error(args ...interface{}) {
@@ -43,20 +46,10 @@ func (t *RuntimeT) Error(args ...interface{}) {
 }
 
 func (t *RuntimeT) Errorf(format string, args ...interface{}) {
-	log.Println(fmt.Sprintf(format, args...))
+	log.Printf(format, args...)
 	t.Fail()
 }
 
-func (t *RuntimeT) Fatal(args ...interface{}) {
-	log.Println(fmt.Sprintln(args...))
-	t.FailNow()
-}
-
-func (t *RuntimeT) Fatalf(format string, args ...interface{}) {
-	log.Println(fmt.Sprintf(format, args...))
-	t.FailNow()
-}
-
 func (t *RuntimeT) Fail() {
 	t.failed = true
 }
@@ -69,6 +62,16 @@ func (t *RuntimeT) Failed() bool {
 	return t.failed
 }
 
+func (t *RuntimeT) Fatal(args ...interface{}) {
+	log.Print(args...)
+	t.FailNow()
+}
+
+func (t *RuntimeT) Fatalf(format string, args ...interface{}) {
+	log.Printf(format, args...)
+	t.FailNow()
+}
+
 func (t *RuntimeT) Log(args ...interface{}) {
 	log.Println(fmt.Sprintln(args...))
 }
@@ -77,8 +80,28 @@ func (t *RuntimeT) Logf(format string, args ...interface{}) {
 	log.Println(fmt.Sprintf(format, args...))
 }
 
-func (t *RuntimeT) Name() string                             { return "" }
-func (t *RuntimeT) Skip(args ...interface{})                 {}
-func (t *RuntimeT) SkipNow()                                 {}
-func (t *RuntimeT) Skipf(format string, args ...interface{}) {}
-func (t *RuntimeT) Skipped() bool                            { return false }
+func (t *RuntimeT) Name() string {
+	return ""
+}
+
+func (t *RuntimeT) Skip(args ...interface{}) {
+	log.Print(args...)
+	t.SkipNow()
+}
+
+func (t *RuntimeT) SkipNow() {
+	t.skipped = true
+}
+
+func (t *RuntimeT) Skipf(format string, args ...interface{}) {
+	log.Printf(format, args...)
+	t.SkipNow()
+}
+
+func (t *RuntimeT) Skipped() bool {
+	return t.skipped
+}
+
+func (t *RuntimeT) Helper() {}
+
+func (t *RuntimeT) Cleanup(func()) {}
diff --git a/testing_go19.go b/testing_go19.go
deleted file mode 100644
index 31b42ca..0000000
--- a/testing_go19.go
+++ /dev/null
@@ -1,108 +0,0 @@
-// +build go1.9
-
-// NOTE: This is a temporary copy of testing.go for Go 1.9 with the addition
-// of "Helper" to the T interface. Go 1.9 at the time of typing is in RC
-// and is set for release shortly. We'll support this on master as the default
-// as soon as 1.9 is released.
-
-package testing
-
-import (
-	"fmt"
-	"log"
-)
-
-// T is the interface that mimics the standard library *testing.T.
-//
-// In unit tests you can just pass a *testing.T struct. At runtime, outside
-// of tests, you can pass in a RuntimeT struct from this package.
-type T interface {
-	Error(args ...interface{})
-	Errorf(format string, args ...interface{})
-	Fail()
-	FailNow()
-	Failed() bool
-	Fatal(args ...interface{})
-	Fatalf(format string, args ...interface{})
-	Log(args ...interface{})
-	Logf(format string, args ...interface{})
-	Name() string
-	Skip(args ...interface{})
-	SkipNow()
-	Skipf(format string, args ...interface{})
-	Skipped() bool
-	Helper()
-}
-
-// RuntimeT implements T and can be instantiated and run at runtime to
-// mimic *testing.T behavior. Unlike *testing.T, this will simply panic
-// for calls to Fatal. For calls to Error, you'll have to check the errors
-// list to determine whether to exit yourself.
-type RuntimeT struct {
-	skipped bool
-	failed  bool
-}
-
-func (t *RuntimeT) Error(args ...interface{}) {
-	log.Println(fmt.Sprintln(args...))
-	t.Fail()
-}
-
-func (t *RuntimeT) Errorf(format string, args ...interface{}) {
-	log.Printf(format, args...)
-	t.Fail()
-}
-
-func (t *RuntimeT) Fail() {
-	t.failed = true
-}
-
-func (t *RuntimeT) FailNow() {
-	panic("testing.T failed, see logs for output (if any)")
-}
-
-func (t *RuntimeT) Failed() bool {
-	return t.failed
-}
-
-func (t *RuntimeT) Fatal(args ...interface{}) {
-	log.Print(args...)
-	t.FailNow()
-}
-
-func (t *RuntimeT) Fatalf(format string, args ...interface{}) {
-	log.Printf(format, args...)
-	t.FailNow()
-}
-
-func (t *RuntimeT) Log(args ...interface{}) {
-	log.Println(fmt.Sprintln(args...))
-}
-
-func (t *RuntimeT) Logf(format string, args ...interface{}) {
-	log.Println(fmt.Sprintf(format, args...))
-}
-
-func (t *RuntimeT) Name() string {
-	return ""
-}
-
-func (t *RuntimeT) Skip(args ...interface{}) {
-	log.Print(args...)
-	t.SkipNow()
-}
-
-func (t *RuntimeT) SkipNow() {
-	t.skipped = true
-}
-
-func (t *RuntimeT) Skipf(format string, args ...interface{}) {
-	log.Printf(format, args...)
-	t.SkipNow()
-}
-
-func (t *RuntimeT) Skipped() bool {
-	return t.skipped
-}
-
-func (t *RuntimeT) Helper() {}