diff --git a/internal/errors/runtime.go b/internal/errors/runtime.go
index 74add69e88..380006fb32 100644
--- a/internal/errors/runtime.go
+++ b/internal/errors/runtime.go
@@ -20,16 +20,17 @@ package errors
 import "runtime"
 
 var (
-	// Runtime.
-
+	// ErrPanicRecovered represents a function to generate an error that the panic recovered.
 	ErrPanicRecovered = func(err error, rec interface{}) error {
 		return Wrap(err, Errorf("panic recovered: %v", rec).Error())
 	}
 
+	// ErrPanicString represents a function to generate an error that the panic recovered with a string message.
 	ErrPanicString = func(err error, msg string) error {
 		return Wrap(err, Errorf("panic recovered: %v", msg).Error())
 	}
 
+	// ErrRuntimeError represents a function to generate an error that the panic caused by runtime error.
 	ErrRuntimeError = func(err error, r runtime.Error) error {
 		return Wrap(err, Errorf("system panicked caused by runtime error: %v", r).Error())
 	}
diff --git a/internal/errors/runtime_test.go b/internal/errors/runtime_test.go
new file mode 100644
index 0000000000..ea40d9a6af
--- /dev/null
+++ b/internal/errors/runtime_test.go
@@ -0,0 +1,431 @@
+//
+// Copyright (C) 2019-2021 vdaas.org vald team <vald@vdaas.org>
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package errors
+
+import (
+	"math"
+	"runtime"
+	"testing"
+	"time"
+
+	"go.uber.org/goleak"
+)
+
+func TestErrPanicRecovered(t *testing.T) {
+	t.Parallel()
+	type args struct {
+		err error
+		rec interface{}
+	}
+	type want struct {
+		want error
+	}
+	type test struct {
+		name       string
+		args       args
+		want       want
+		checkFunc  func(want, error) error
+		beforeFunc func(args)
+		afterFunc  func(args)
+	}
+	defaultCheckFunc := func(w want, got error) error {
+		if !Is(got, w.want) {
+			return Errorf("got: \"%#v\",\n\t\twant: \"%#v\"", got, w.want)
+		}
+		return nil
+	}
+	defaultErr := New("runtime error")
+	tests := []test{
+		func() test {
+			r := math.MaxFloat64
+			return test{
+				name: "return an error when err is not empty and rec is int value",
+				args: args{
+					err: defaultErr,
+					rec: r,
+				},
+				want: want{
+					want: Wrap(defaultErr, Errorf("panic recovered: %v", r).Error()),
+				},
+			}
+		}(),
+		func() test {
+			r := math.MaxFloat64
+			return test{
+				name: "return an error when err is not empty and rec is float value",
+				args: args{
+					err: defaultErr,
+					rec: r,
+				},
+				want: want{
+					want: Wrap(defaultErr, Errorf("panic recovered: %v", r).Error()),
+				},
+			}
+		}(),
+		func() test {
+			tString := "10h"
+			var r time.Duration
+			r, _ = time.ParseDuration(tString)
+			return test{
+				name: "return an error when err is not empty and rec is time.Duration value",
+				args: args{
+					err: defaultErr,
+					rec: r,
+				},
+				want: want{
+					want: Wrap(defaultErr, Errorf("panic recovered: %v", r).Error()),
+				},
+			}
+		}(),
+		func() test {
+			r := "10h"
+			return test{
+				name: "return an error when err is not empty and rec is string value",
+				args: args{
+					err: defaultErr,
+					rec: r,
+				},
+				want: want{
+					want: Wrap(defaultErr, Errorf("panic recovered: %v", r).Error()),
+				},
+			}
+		}(),
+		func() test {
+			r := []byte{0x00, 0x01}
+			return test{
+				name: "return an error when err is not empty and rec is byte slice value",
+				args: args{
+					err: defaultErr,
+					rec: r,
+				},
+				want: want{
+					want: Wrap(defaultErr, Errorf("panic recovered: %v", r).Error()),
+				},
+			}
+		}(),
+		func() test {
+			r := struct {
+				connectionType string
+				code           int
+			}{
+				connectionType: "grpc",
+				code:           404,
+			}
+			return test{
+				name: "return an error when err is not empty and rec is struct value",
+				args: args{
+					err: defaultErr,
+					rec: r,
+				},
+				want: want{
+					want: Wrap(defaultErr, Errorf("panic recovered: %v", r).Error()),
+				},
+			}
+		}(),
+		func() test {
+			r := map[string]int{
+				"uuid": 12345678,
+			}
+			return test{
+				name: "return an error when err is not empty and rec is map value",
+				args: args{
+					err: defaultErr,
+					rec: r,
+				},
+				want: want{
+					want: Wrap(defaultErr, Errorf("panic recovered: %v", r).Error()),
+				},
+			}
+		}(),
+		func() test {
+			r := true
+			return test{
+				name: "return an error when err is not empty and rec is boolean",
+				args: args{
+					err: defaultErr,
+					rec: r,
+				},
+				want: want{
+					want: Wrap(defaultErr, Errorf("panic recovered: %v", r).Error()),
+				},
+			}
+		}(),
+		func() test {
+			r := &defaultErr
+			return test{
+				name: "return an error when err is not empty and rec is pointer",
+				args: args{
+					err: defaultErr,
+					rec: r,
+				},
+				want: want{
+					want: Wrap(defaultErr, Errorf("panic recovered: %v", r).Error()),
+				},
+			}
+		}(),
+		func() test {
+			r := "10h"
+			return test{
+				name: "return an error when err is empty and rec has value",
+				args: args{
+					rec: r,
+				},
+				want: want{
+					want: Wrap(nil, Errorf("panic recovered: %v", r).Error()),
+				},
+			}
+		}(),
+		func() test {
+			return test{
+				name: "return an error when err is not empty and rec is nil",
+				args: args{
+					err: defaultErr,
+				},
+				want: want{
+					want: Wrap(defaultErr, Errorf("panic recovered: %v", nil).Error()),
+				},
+			}
+		}(),
+		func() test {
+			return test{
+				name: "return an error when err and rec are empty or nil",
+				args: args{},
+				want: want{
+					want: Wrap(nil, Errorf("panic recovered: %v", nil).Error()),
+				},
+			}
+		}(),
+	}
+	for _, tc := range tests {
+		test := tc
+		t.Run(test.name, func(tt *testing.T) {
+			tt.Parallel()
+			defer goleak.VerifyNone(tt, goleak.IgnoreCurrent())
+			if test.beforeFunc != nil {
+				test.beforeFunc(test.args)
+			}
+			if test.afterFunc != nil {
+				defer test.afterFunc(test.args)
+			}
+			if test.checkFunc == nil {
+				test.checkFunc = defaultCheckFunc
+			}
+
+			got := ErrPanicRecovered(test.args.err, test.args.rec)
+			if err := test.checkFunc(test.want, got); err != nil {
+				tt.Errorf("error = %v", err)
+			}
+		})
+	}
+}
+
+func TestErrPanicString(t *testing.T) {
+	t.Parallel()
+	type args struct {
+		err error
+		msg string
+	}
+	type want struct {
+		want error
+	}
+	type test struct {
+		name       string
+		args       args
+		want       want
+		checkFunc  func(want, error) error
+		beforeFunc func(args)
+		afterFunc  func(args)
+	}
+	defaultCheckFunc := func(w want, got error) error {
+		if !Is(got, w.want) {
+			return Errorf("got: \"%#v\",\n\t\t\t\twant: \"%#v\"", got, w.want)
+		}
+		return nil
+	}
+	defaultErr := New("runtime panic string error")
+	defaultMsg := "success"
+	tests := []test{
+		func() test {
+			return test{
+				name: "return an error when err is not nil and msg is not empty",
+				args: args{
+					err: defaultErr,
+					msg: defaultMsg,
+				},
+				want: want{
+					want: Wrap(defaultErr, Errorf("panic recovered: %v", defaultMsg).Error()),
+				},
+			}
+		}(),
+		func() test {
+			return test{
+				name: "return an error when err is not nil and msg is empty",
+				args: args{
+					err: defaultErr,
+				},
+				want: want{
+					want: Wrap(defaultErr, New("panic recovered: ").Error()),
+				},
+			}
+		}(),
+		func() test {
+			return test{
+				name: "return an error when err is nil and msg is not empty",
+				args: args{
+					msg: defaultMsg,
+				},
+				want: want{
+					want: Wrap(nil, Errorf("panic recovered: %v", defaultMsg).Error()),
+				},
+			}
+		}(),
+		func() test {
+			return test{
+				name: "return an error when err is nil and msg is empty",
+				args: args{},
+				want: want{
+					want: Wrap(nil, New("panic recovered: ").Error()),
+				},
+			}
+		}(),
+	}
+	for _, tc := range tests {
+		test := tc
+		t.Run(test.name, func(tt *testing.T) {
+			tt.Parallel()
+			defer goleak.VerifyNone(tt, goleak.IgnoreCurrent())
+			if test.beforeFunc != nil {
+				test.beforeFunc(test.args)
+			}
+			if test.afterFunc != nil {
+				defer test.afterFunc(test.args)
+			}
+			if test.checkFunc == nil {
+				test.checkFunc = defaultCheckFunc
+			}
+
+			got := ErrPanicString(test.args.err, test.args.msg)
+			if err := test.checkFunc(test.want, got); err != nil {
+				tt.Errorf("error = %v", err)
+			}
+		})
+	}
+}
+
+type runtimeErr struct {
+	err error
+}
+
+func (e runtimeErr) RuntimeError() {}
+func (e runtimeErr) Error() string {
+	return e.err.Error()
+}
+
+func TestErrRuntimeError(t *testing.T) {
+	t.Parallel()
+	type args struct {
+		err error
+		r   runtime.Error
+	}
+	type want struct {
+		want error
+	}
+	type test struct {
+		name       string
+		args       args
+		want       want
+		checkFunc  func(want, error) error
+		beforeFunc func(args)
+		afterFunc  func(args)
+	}
+	defaultCheckFunc := func(w want, got error) error {
+		if !Is(got, w.want) {
+			return Errorf("got: \"%#v\",\n\t\t\t\twant: \"%#v\"", got, w.want)
+		}
+		return nil
+	}
+	defaultErr := New("runtime panic string error")
+	defaultRuntimeErr := &runtimeErr{
+		err: New("runtime error is occurred"),
+	}
+	tests := []test{
+		func() test {
+			return test{
+				name: "return an error when err is not nil and r is not empty",
+				args: args{
+					err: defaultErr,
+					r:   defaultRuntimeErr,
+				},
+				want: want{
+					want: Wrap(defaultErr, Errorf("system panicked caused by runtime error: %v", defaultRuntimeErr).Error()),
+				},
+			}
+		}(),
+		func() test {
+			return test{
+				name: "return an error when err is not nil and msg is nil",
+				args: args{
+					err: defaultErr,
+				},
+				want: want{
+					want: Wrap(defaultErr, Errorf("system panicked caused by runtime error: %v", nil).Error()),
+				},
+			}
+		}(),
+		func() test {
+			return test{
+				name: "return an error when err is nil and msg is not empty",
+				args: args{
+					r: defaultRuntimeErr,
+				},
+				want: want{
+					want: Wrap(nil, Errorf("system panicked caused by runtime error: %v", defaultRuntimeErr).Error()),
+				},
+			}
+		}(),
+		func() test {
+			return test{
+				name: "return an error when err is nil and msg is nil",
+				args: args{},
+				want: want{
+					want: Wrap(nil, Errorf("system panicked caused by runtime error: %v", nil).Error()),
+				},
+			}
+		}(),
+	}
+	for _, tc := range tests {
+		test := tc
+		t.Run(test.name, func(tt *testing.T) {
+			tt.Parallel()
+			defer goleak.VerifyNone(tt, goleak.IgnoreCurrent())
+			if test.beforeFunc != nil {
+				test.beforeFunc(test.args)
+			}
+			if test.afterFunc != nil {
+				defer test.afterFunc(test.args)
+			}
+			if test.checkFunc == nil {
+				test.checkFunc = defaultCheckFunc
+			}
+
+			got := ErrRuntimeError(test.args.err, test.args.r)
+			if err := test.checkFunc(test.want, got); err != nil {
+				tt.Errorf("error = %v", err)
+			}
+		})
+	}
+}