diff --git a/studyplus-android-sdk2/build.gradle b/studyplus-android-sdk2/build.gradle
index cf4f423..429df57 100644
--- a/studyplus-android-sdk2/build.gradle
+++ b/studyplus-android-sdk2/build.gradle
@@ -50,7 +50,6 @@ dependencies {
 
     testImplementation 'junit:junit:4.12'
     testImplementation 'org.robolectric:robolectric:4.0.2'
-    testImplementation 'org.json:json:20180813'
     testImplementation "org.jetbrains.kotlin:kotlin-test-junit:$kotlin_version"
     testImplementation "com.squareup.okhttp3:mockwebserver:$okhttp"
 }
diff --git a/studyplus-android-sdk2/src/test/java/jp/studyplus/android/sdk/StudyRecordUnitTest.kt b/studyplus-android-sdk2/src/test/java/jp/studyplus/android/sdk/StudyRecordUnitTest.kt
index 8da48cf..6e45c02 100644
--- a/studyplus-android-sdk2/src/test/java/jp/studyplus/android/sdk/StudyRecordUnitTest.kt
+++ b/studyplus-android-sdk2/src/test/java/jp/studyplus/android/sdk/StudyRecordUnitTest.kt
@@ -5,8 +5,11 @@ import jp.studyplus.android.sdk.record.StudyRecordAmountRange
 import jp.studyplus.android.sdk.record.StudyRecordAmountTotal
 import org.junit.Assert.assertEquals
 import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
 import java.util.*
 
+@RunWith(RobolectricTestRunner::class)
 class StudyRecordUnitTest {
 
     @Test
@@ -14,7 +17,7 @@ class StudyRecordUnitTest {
         val studyRecord = StudyRecord(2 * 60)
 
         assertEquals(
-            "{\"duration\":120,\"recorded_at\":\"${StudyRecord.formatTime(studyRecord.recordedTime)}\"}",
+            "{\"recorded_at\":\"${StudyRecord.formatTime(studyRecord.recordedTime)}\",\"duration\":120}",
             studyRecord.toJson()
         )
     }
@@ -29,7 +32,7 @@ class StudyRecordUnitTest {
         )
 
         assertEquals(
-            "{\"duration\":120,\"recorded_at\":\"2019-06-01 01:02:03\",\"amount\":30,\"comment\":\"perfect!\"}",
+            "{\"recorded_at\":\"2019-06-01 01:02:03\",\"duration\":120,\"comment\":\"perfect!\",\"amount\":30}",
             studyRecord.toJson()
         )
     }
@@ -44,7 +47,7 @@ class StudyRecordUnitTest {
         )
 
         assertEquals(
-            "{\"duration\":120,\"start_position\":5,\"recorded_at\":\"2019-06-01 01:02:03\",\"comment\":\"perfect!\",\"end_position\":12}",
+            "{\"recorded_at\":\"2019-06-01 01:02:03\",\"duration\":120,\"comment\":\"perfect!\",\"start_position\":5,\"end_position\":12}",
             studyRecord.toJson()
         )
     }