diff --git a/internal/rate/rate_test.go b/internal/rate/rate_test.go
index 5c5523e0..36ce0e08 100644
--- a/internal/rate/rate_test.go
+++ b/internal/rate/rate_test.go
@@ -13,7 +13,7 @@ const (
 	defaultBufSize               = 4096
 )
 
-func getExpectCost(dataSize, bytesPerSecond int64) (expectCost time.Duration, max time.Duration, min time.Duration) {
+func getExpectCost(dataSize, bytesPerSecond int64) (expectCost time.Duration, maxCost time.Duration, minCost time.Duration) {
 	expectCost = time.Second * time.Duration(dataSize) / time.Duration(bytesPerSecond)
 
 	if bytesPerSecond <= defaultBufSize && dataSize <= defaultBufSize {
@@ -21,19 +21,19 @@ func getExpectCost(dataSize, bytesPerSecond int64) (expectCost time.Duration, ma
 	} else if bytesPerSecond > defaultBufSize && dataSize <= defaultBufSize {
 		expectCost = 0
 	}
-	max = expectCost * (100 + deviation) / 100
-	min = expectCost * (100 - deviation) / 100
+	maxCost = expectCost * (100 + deviation) / 100
+	minCost = expectCost * (100 - deviation) / 100
 	// the minimum deviation time is 1 second
-	if expectCost-min < time.Second {
-		min = expectCost - time.Second
+	if expectCost-minCost < time.Second {
+		minCost = expectCost - time.Second
 	}
-	if min < 0 {
-		min = 0
+	if minCost < 0 {
+		minCost = 0
 	}
-	if max <= 0 {
-		max = time.Second * deviation / 100
+	if maxCost <= 0 {
+		maxCost = time.Second * deviation / 100
 	}
-	return expectCost, max, min
+	return expectCost, maxCost, minCost
 }
 
 type writer struct {
diff --git a/internal/rate/reader_at_test.go b/internal/rate/reader_at_test.go
index aac48d52..086452a1 100644
--- a/internal/rate/reader_at_test.go
+++ b/internal/rate/reader_at_test.go
@@ -57,16 +57,16 @@ func TestReadAt(t *testing.T) {
 				return
 			}
 
-			expectCost, max, min := getExpectCost(tc.dataSize, tc.bytesPerSecond)
+			expectCost, maxCost, minCost := getExpectCost(tc.dataSize, tc.bytesPerSecond)
 			actualCost := end.Sub(start)
-			if actualCost >= min && actualCost <= max {
+			if actualCost >= minCost && actualCost <= maxCost {
 				rate := 0.0
 				if actualCost > 0 {
 					rate = float64(tc.dataSize) / actualCost.Seconds()
 				}
 				t.Logf("[%s] dataSize=%d bytesPerSecond=%d cost=%s, rate=%.2f bytes/sec", tc.name, tc.dataSize, tc.bytesPerSecond, actualCost, rate)
 			} else {
-				t.Errorf("[%s] dataSize=%d bytesPerSecond=%d expect cost=%s min=%s max=%s, but actual cost=%s", tc.name, tc.dataSize, tc.bytesPerSecond, expectCost, min, max, actualCost)
+				t.Errorf("[%s] dataSize=%d bytesPerSecond=%d expect cost=%s min=%s max=%s, but actual cost=%s", tc.name, tc.dataSize, tc.bytesPerSecond, expectCost, minCost, maxCost, actualCost)
 			}
 		})
 	}
diff --git a/internal/rate/reader_test.go b/internal/rate/reader_test.go
index 52ad3b98..8707f22a 100644
--- a/internal/rate/reader_test.go
+++ b/internal/rate/reader_test.go
@@ -43,16 +43,16 @@ func TestReader(t *testing.T) {
 				return
 			}
 
-			expectCost, max, min := getExpectCost(tc.dataSize, tc.bytesPerSecond)
+			expectCost, maxCost, minCost := getExpectCost(tc.dataSize, tc.bytesPerSecond)
 			actualCost := end.Sub(start)
-			if actualCost >= min && actualCost <= max {
+			if actualCost >= minCost && actualCost <= maxCost {
 				rate := 0.0
 				if actualCost > 0 {
 					rate = float64(tc.dataSize) / actualCost.Seconds()
 				}
 				t.Logf("[%s] dataSize=%d bytesPerSecond=%d cost=%s, rate=%.2f bytes/sec", tc.name, tc.dataSize, tc.bytesPerSecond, actualCost, rate)
 			} else {
-				t.Errorf("[%s] dataSize=%d bytesPerSecond=%d expect cost=%s min=%s max=%s, but actual cost=%s", tc.name, tc.dataSize, tc.bytesPerSecond, expectCost, min, max, actualCost)
+				t.Errorf("[%s] dataSize=%d bytesPerSecond=%d expect cost=%s min=%s max=%s, but actual cost=%s", tc.name, tc.dataSize, tc.bytesPerSecond, expectCost, minCost, maxCost, actualCost)
 			}
 		})
 	}