diff --git a/tfexec/terraform_version_test.go b/tfexec/terraform_version_test.go
index 61adddb..5aca27f 100644
--- a/tfexec/terraform_version_test.go
+++ b/tfexec/terraform_version_test.go
@@ -5,6 +5,8 @@ import (
 	"fmt"
 	"os"
 	"testing"
+
+	"github.com/hashicorp/go-version"
 )
 
 func TestTerraformCLIVersion(t *testing.T) {
@@ -87,3 +89,44 @@ func TestAccTerraformCLIVersion(t *testing.T) {
 	}
 	fmt.Printf("got = %s\n", got)
 }
+
+func TestTruncatePreReleaseVersion(t *testing.T) {
+	cases := []struct {
+		desc string
+		v    string
+		want string
+		ok   bool
+	}{
+		{
+			desc: "pre-release",
+			v:    "1.6.0-rc1",
+			want: "1.6.0",
+			ok:   true,
+		},
+		{
+			desc: "not pre-release",
+			v:    "1.6.0",
+			want: "1.6.0",
+			ok:   true,
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.desc, func(t *testing.T) {
+			v, err := version.NewVersion(tc.v)
+			if err != nil {
+				t.Fatalf("failed to parse version: %s", err)
+			}
+			got, err := truncatePreReleaseVersion(v)
+			if tc.ok && err != nil {
+				t.Fatalf("unexpected err: %s", err)
+			}
+			if !tc.ok && err == nil {
+				t.Fatalf("expected to return an error, but no error, got = %s", got)
+			}
+			if tc.ok && got.String() != tc.want {
+				t.Errorf("got: %s, want: %s", got, tc.want)
+			}
+		})
+	}
+}
diff --git a/tfmigrate/test_helper.go b/tfmigrate/test_helper.go
index 92a0de0..1660adc 100644
--- a/tfmigrate/test_helper.go
+++ b/tfmigrate/test_helper.go
@@ -6,28 +6,6 @@ import "regexp"
 // error message for missing bucket key in the s3 backend differs
 // depending on the Terraform version.
 // Define a helper function to hide the difference.
-//
-// # Terraform v1.5
-//
-// ```
-// Error: "bucket": required field is not set
-// ```
-//
-// # Terraform v1.6
-//
-// ```
-//
-//	Error: Missing Required Value
-//
-//	  on main.tf line 4, in terraform:
-//	   4:   backend "s3" {
-//
-//	The attribute "bucket" is required by the backend.
-//
-//	Refer to the backend documentation for additional information which
-//	attributes are required.
-//
-// ```
 const testBucketRequiredErrorLegacyTF = `Error: "bucket": required field is not set`
 const testBucketRequiredErrorTF16 = `The attribute "bucket" is required by the backend`
 
diff --git a/tfmigrate/test_helper_test.go b/tfmigrate/test_helper_test.go
new file mode 100644
index 0000000..3c50c59
--- /dev/null
+++ b/tfmigrate/test_helper_test.go
@@ -0,0 +1,50 @@
+package tfmigrate
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestContainsBucketRequiredError(t *testing.T) {
+	cases := []struct {
+		desc string
+		msg  string
+		want bool
+	}{
+		{
+			desc: "terraform v1.5",
+			msg:  `Error: "bucket": required field is not set`,
+			want: true,
+		},
+		{
+			desc: "terraform v1.6",
+			msg: `
+Error: Missing Required Value
+
+  on main.tf line 4, in terraform:
+   4:   backend "s3" {
+
+The attribute "bucket" is required by the backend.
+
+Refer to the backend documentation for additional information which
+attributes are required.
+
+`,
+			want: true,
+		},
+		{
+			desc: "unknown",
+			msg:  `Error: unknown`,
+			want: false,
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.desc, func(t *testing.T) {
+			got := containsBucketRequiredError(errors.New(tc.msg))
+			if got != tc.want {
+				t.Errorf("got: %t, want: %t", got, tc.want)
+			}
+		})
+	}
+}