diff --git a/builtin/assertion.go b/builtin/assertion.go
index 99782626..ca290aa8 100644
--- a/builtin/assertion.go
+++ b/builtin/assertion.go
@@ -1,6 +1,9 @@
 package builtin
 
 import (
+	"fmt"
+	"strings"
+
 	"github.com/stretchr/testify/assert"
 )
 
@@ -15,10 +18,36 @@ var Assertions = map[string]func(t assert.TestingT, expected interface{}, actual
 	"contains":          assert.Contains,
 	"regex_match":       assert.Regexp,
 	// custom assertions
+	"startswith":    StartsWith, // check if string starts with substring
+	"endswith":      EndsWith,   // check if string ends with substring
 	"length_equals": EqualLength,
 	"length_equal":  EqualLength, // alias for length_equals
 }
 
+func StartsWith(t assert.TestingT, expected, actual interface{}, msgAndArgs ...interface{}) bool {
+	if !assert.IsType(t, "string", actual, fmt.Sprintf("actual is %v", actual)) {
+		return false
+	}
+	if !assert.IsType(t, "string", expected, fmt.Sprintf("expected is %v", expected)) {
+		return false
+	}
+	actualString := actual.(string)
+	expectedString := expected.(string)
+	return assert.True(t, strings.HasPrefix(actualString, expectedString), msgAndArgs...)
+}
+
+func EndsWith(t assert.TestingT, expected, actual interface{}, msgAndArgs ...interface{}) bool {
+	if !assert.IsType(t, "string", actual, fmt.Sprintf("actual is %v", actual)) {
+		return false
+	}
+	if !assert.IsType(t, "string", expected, fmt.Sprintf("expected is %v", expected)) {
+		return false
+	}
+	actualString := actual.(string)
+	expectedString := expected.(string)
+	return assert.True(t, strings.HasSuffix(actualString, expectedString), msgAndArgs...)
+}
+
 func EqualLength(t assert.TestingT, expected, actual interface{}, msgAndArgs ...interface{}) bool {
 	return assert.Len(t, actual, expected.(int), msgAndArgs...)
 }
diff --git a/builtin/assertion_test.go b/builtin/assertion_test.go
new file mode 100644
index 00000000..328839be
--- /dev/null
+++ b/builtin/assertion_test.go
@@ -0,0 +1,43 @@
+package builtin
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestStartsWith(t *testing.T) {
+	testData := []struct {
+		raw      string
+		expected string
+	}{
+		{"", ""},
+		{"a", "a"},
+		{"abc", "a"},
+		{"abc", "ab"},
+	}
+
+	for _, data := range testData {
+		if !assert.True(t, StartsWith(t, data.expected, data.raw)) {
+			t.Fail()
+		}
+	}
+}
+
+func TestEndsWith(t *testing.T) {
+	testData := []struct {
+		raw      string
+		expected string
+	}{
+		{"", ""},
+		{"a", "a"},
+		{"abc", "c"},
+		{"abc", "bc"},
+	}
+
+	for _, data := range testData {
+		if !assert.True(t, EndsWith(t, data.expected, data.raw)) {
+			t.Fail()
+		}
+	}
+}
diff --git a/validate.go b/validate.go
index 4244edb7..d325fe22 100644
--- a/validate.go
+++ b/validate.go
@@ -32,6 +32,28 @@ func (s *stepRequestValidation) AssertEqual(jmesPath string, expected interface{
 	return s
 }
 
+func (s *stepRequestValidation) AssertStartsWith(jmesPath string, expected interface{}, msg string) *stepRequestValidation {
+	validator := TValidator{
+		Check:   jmesPath,
+		Assert:  "startswith",
+		Expect:  expected,
+		Message: msg,
+	}
+	s.step.Validators = append(s.step.Validators, validator)
+	return s
+}
+
+func (s *stepRequestValidation) AssertEndsWith(jmesPath string, expected interface{}, msg string) *stepRequestValidation {
+	validator := TValidator{
+		Check:   jmesPath,
+		Assert:  "endswith",
+		Expect:  expected,
+		Message: msg,
+	}
+	s.step.Validators = append(s.step.Validators, validator)
+	return s
+}
+
 func (s *stepRequestValidation) AssertLengthEqual(jmesPath string, expected interface{}, msg string) *stepRequestValidation {
 	validator := TValidator{
 		Check:   jmesPath,