diff --git a/app/src/main/java/io/github/wulkanowy/data/db/dao/SemesterDao.kt b/app/src/main/java/io/github/wulkanowy/data/db/dao/SemesterDao.kt
index 44de31d85..608a66630 100644
--- a/app/src/main/java/io/github/wulkanowy/data/db/dao/SemesterDao.kt
+++ b/app/src/main/java/io/github/wulkanowy/data/db/dao/SemesterDao.kt
@@ -1,8 +1,8 @@
 package io.github.wulkanowy.data.db.dao
 
 import androidx.room.Dao
+import androidx.room.Delete
 import androidx.room.Insert
-import androidx.room.OnConflictStrategy.IGNORE
 import androidx.room.Query
 import io.github.wulkanowy.data.db.entities.Semester
 import io.reactivex.Maybe
@@ -12,15 +12,12 @@ import javax.inject.Singleton
 @Dao
 interface SemesterDao {
 
-    @Insert(onConflict = IGNORE)
+    @Insert
     fun insertAll(semester: List<Semester>)
 
+    @Delete
+    fun deleteAll(semester: List<Semester>)
+
     @Query("SELECT * FROM Semesters WHERE student_id = :studentId")
     fun loadAll(studentId: Int): Maybe<List<Semester>>
-
-    @Query("UPDATE Semesters SET is_current = 1 WHERE semester_id = :semesterId AND diary_id = :diaryId")
-    fun updateCurrent(semesterId: Int, diaryId: Int)
-
-    @Query("UPDATE Semesters SET is_current = 0 WHERE student_id = :studentId")
-    fun resetCurrent(studentId: Int)
 }
diff --git a/app/src/main/java/io/github/wulkanowy/data/repositories/semester/SemesterLocal.kt b/app/src/main/java/io/github/wulkanowy/data/repositories/semester/SemesterLocal.kt
index 5be82d7f9..37d4a2687 100644
--- a/app/src/main/java/io/github/wulkanowy/data/repositories/semester/SemesterLocal.kt
+++ b/app/src/main/java/io/github/wulkanowy/data/repositories/semester/SemesterLocal.kt
@@ -11,17 +11,14 @@ import javax.inject.Singleton
 class SemesterLocal @Inject constructor(private val semesterDb: SemesterDao) {
 
     fun saveSemesters(semesters: List<Semester>) {
-        return semesterDb.insertAll(semesters)
+        semesterDb.insertAll(semesters)
+    }
+
+    fun deleteSemesters(semesters: List<Semester>) {
+        semesterDb.deleteAll(semesters)
     }
 
     fun getSemesters(student: Student): Maybe<List<Semester>> {
         return semesterDb.loadAll(student.studentId).filter { !it.isEmpty() }
     }
-
-    fun setCurrentSemester(semester: Semester) {
-        semesterDb.run {
-            resetCurrent(semester.studentId)
-            updateCurrent(semester.semesterId, semester.diaryId)
-        }
-    }
 }
diff --git a/app/src/main/java/io/github/wulkanowy/data/repositories/semester/SemesterRepository.kt b/app/src/main/java/io/github/wulkanowy/data/repositories/semester/SemesterRepository.kt
index 975868a22..9735f0290 100644
--- a/app/src/main/java/io/github/wulkanowy/data/repositories/semester/SemesterRepository.kt
+++ b/app/src/main/java/io/github/wulkanowy/data/repositories/semester/SemesterRepository.kt
@@ -7,6 +7,7 @@ import io.github.wulkanowy.data.db.entities.Semester
 import io.github.wulkanowy.data.db.entities.Student
 import io.reactivex.Maybe
 import io.reactivex.Single
+import timber.log.Timber
 import java.net.UnknownHostException
 import javax.inject.Inject
 import javax.inject.Singleton
@@ -25,10 +26,17 @@ class SemesterRepository @Inject constructor(
             .switchIfEmpty(ReactiveNetwork.checkInternetConnectivity(settings)
                 .flatMap {
                     if (it) remote.getSemesters(student) else Single.error(UnknownHostException())
-                }.map { newSemesters ->
-                    local.apply {
-                        saveSemesters(newSemesters)
-                        setCurrentSemester(newSemesters.single { it.isCurrent })
+                }.flatMap { new ->
+                    val currentSemesters = new.filter { it.isCurrent }
+                    if (currentSemesters.size == 1) {
+                        local.getSemesters(student).toSingle(emptyList())
+                            .doOnSuccess { old ->
+                                local.deleteSemesters(old - new)
+                                local.saveSemesters(new - old)
+                            }
+                    } else {
+                        Timber.i("Current semesters list:\n${currentSemesters.joinToString(separator = "\n")}")
+                        throw IllegalArgumentException("Current semester can be only one.")
                     }
                 }.flatMap { local.getSemesters(student).toSingle(emptyList()) })
     }
diff --git a/app/src/test/java/io/github/wulkanowy/data/repositories/UnitTestInternetObservingStrategy.kt b/app/src/test/java/io/github/wulkanowy/data/repositories/UnitTestInternetObservingStrategy.kt
new file mode 100644
index 000000000..28abbb993
--- /dev/null
+++ b/app/src/test/java/io/github/wulkanowy/data/repositories/UnitTestInternetObservingStrategy.kt
@@ -0,0 +1,19 @@
+package io.github.wulkanowy.data.repositories
+
+import com.github.pwittchen.reactivenetwork.library.rx2.internet.observing.InternetObservingStrategy
+import com.github.pwittchen.reactivenetwork.library.rx2.internet.observing.error.ErrorHandler
+import io.reactivex.Observable
+import io.reactivex.Single
+
+class UnitTestInternetObservingStrategy : InternetObservingStrategy {
+
+    override fun checkInternetConnectivity(host: String?, port: Int, timeoutInMs: Int, httpResponse: Int, errorHandler: ErrorHandler?): Single<Boolean> {
+        return Single.just(true)
+    }
+
+    override fun observeInternetConnectivity(initialIntervalInMs: Int, intervalInMs: Int, host: String?, port: Int, timeoutInMs: Int, httpResponse: Int, errorHandler: ErrorHandler?): Observable<Boolean> {
+        return Observable.just(true)
+    }
+
+    override fun getDefaultPingHost() = "localhost"
+}
diff --git a/app/src/test/java/io/github/wulkanowy/data/repositories/remote/AttendanceRemoteTest.kt b/app/src/test/java/io/github/wulkanowy/data/repositories/attendance/AttendanceRemoteTest.kt
similarity index 92%
rename from app/src/test/java/io/github/wulkanowy/data/repositories/remote/AttendanceRemoteTest.kt
rename to app/src/test/java/io/github/wulkanowy/data/repositories/attendance/AttendanceRemoteTest.kt
index 4842d305c..8adfa83bd 100644
--- a/app/src/test/java/io/github/wulkanowy/data/repositories/remote/AttendanceRemoteTest.kt
+++ b/app/src/test/java/io/github/wulkanowy/data/repositories/attendance/AttendanceRemoteTest.kt
@@ -1,9 +1,8 @@
-package io.github.wulkanowy.data.repositories.remote
+package io.github.wulkanowy.data.repositories.attendance
 
 import io.github.wulkanowy.api.Api
 import io.github.wulkanowy.api.attendance.Attendance
 import io.github.wulkanowy.data.db.entities.Semester
-import io.github.wulkanowy.data.repositories.attendance.AttendanceRemote
 import io.mockk.MockKAnnotations
 import io.mockk.every
 import io.mockk.impl.annotations.MockK
diff --git a/app/src/test/java/io/github/wulkanowy/data/repositories/remote/CompletedLessonsRemoteTest.kt b/app/src/test/java/io/github/wulkanowy/data/repositories/completedlessons/CompletedLessonsRemoteTest.kt
similarity index 91%
rename from app/src/test/java/io/github/wulkanowy/data/repositories/remote/CompletedLessonsRemoteTest.kt
rename to app/src/test/java/io/github/wulkanowy/data/repositories/completedlessons/CompletedLessonsRemoteTest.kt
index f4c161bc4..bb9f52945 100644
--- a/app/src/test/java/io/github/wulkanowy/data/repositories/remote/CompletedLessonsRemoteTest.kt
+++ b/app/src/test/java/io/github/wulkanowy/data/repositories/completedlessons/CompletedLessonsRemoteTest.kt
@@ -1,9 +1,8 @@
-package io.github.wulkanowy.data.repositories.remote
+package io.github.wulkanowy.data.repositories.completedlessons
 
 import io.github.wulkanowy.api.Api
 import io.github.wulkanowy.api.timetable.CompletedLesson
 import io.github.wulkanowy.data.db.entities.Semester
-import io.github.wulkanowy.data.repositories.completedlessons.CompletedLessonsRemote
 import io.mockk.MockKAnnotations
 import io.mockk.every
 import io.mockk.impl.annotations.MockK
diff --git a/app/src/test/java/io/github/wulkanowy/data/repositories/remote/ExamRemoteTest.kt b/app/src/test/java/io/github/wulkanowy/data/repositories/exam/ExamRemoteTest.kt
similarity index 93%
rename from app/src/test/java/io/github/wulkanowy/data/repositories/remote/ExamRemoteTest.kt
rename to app/src/test/java/io/github/wulkanowy/data/repositories/exam/ExamRemoteTest.kt
index 0cc785482..0c83bed0a 100644
--- a/app/src/test/java/io/github/wulkanowy/data/repositories/remote/ExamRemoteTest.kt
+++ b/app/src/test/java/io/github/wulkanowy/data/repositories/exam/ExamRemoteTest.kt
@@ -1,9 +1,8 @@
-package io.github.wulkanowy.data.repositories.remote
+package io.github.wulkanowy.data.repositories.exam
 
 import io.github.wulkanowy.api.Api
 import io.github.wulkanowy.api.exams.Exam
 import io.github.wulkanowy.data.db.entities.Semester
-import io.github.wulkanowy.data.repositories.exam.ExamRemote
 import io.mockk.MockKAnnotations
 import io.mockk.every
 import io.mockk.impl.annotations.MockK
diff --git a/app/src/test/java/io/github/wulkanowy/data/repositories/remote/GradeStatisticsRemoteTest.kt b/app/src/test/java/io/github/wulkanowy/data/repositories/gradestatistics/GradeStatisticsRemoteTest.kt
similarity index 91%
rename from app/src/test/java/io/github/wulkanowy/data/repositories/remote/GradeStatisticsRemoteTest.kt
rename to app/src/test/java/io/github/wulkanowy/data/repositories/gradestatistics/GradeStatisticsRemoteTest.kt
index 14381791d..37d3f2ad6 100644
--- a/app/src/test/java/io/github/wulkanowy/data/repositories/remote/GradeStatisticsRemoteTest.kt
+++ b/app/src/test/java/io/github/wulkanowy/data/repositories/gradestatistics/GradeStatisticsRemoteTest.kt
@@ -1,9 +1,8 @@
-package io.github.wulkanowy.data.repositories.remote
+package io.github.wulkanowy.data.repositories.gradestatistics
 
 import io.github.wulkanowy.api.Api
 import io.github.wulkanowy.api.grades.GradeStatistics
 import io.github.wulkanowy.data.db.entities.Semester
-import io.github.wulkanowy.data.repositories.gradestatistics.GradeStatisticsRemote
 import io.mockk.MockKAnnotations
 import io.mockk.every
 import io.mockk.impl.annotations.MockK
diff --git a/app/src/test/java/io/github/wulkanowy/data/repositories/remote/LuckyNumberRemoteTest.kt b/app/src/test/java/io/github/wulkanowy/data/repositories/luckynumber/LuckyNumberRemoteTest.kt
similarity index 95%
rename from app/src/test/java/io/github/wulkanowy/data/repositories/remote/LuckyNumberRemoteTest.kt
rename to app/src/test/java/io/github/wulkanowy/data/repositories/luckynumber/LuckyNumberRemoteTest.kt
index 054f8890d..67e6c2ef6 100644
--- a/app/src/test/java/io/github/wulkanowy/data/repositories/remote/LuckyNumberRemoteTest.kt
+++ b/app/src/test/java/io/github/wulkanowy/data/repositories/luckynumber/LuckyNumberRemoteTest.kt
@@ -1,4 +1,4 @@
-package io.github.wulkanowy.data.repositories.remote
+package io.github.wulkanowy.data.repositories.luckynumber
 
 import io.github.wulkanowy.api.Api
 import io.github.wulkanowy.data.db.entities.Semester
diff --git a/app/src/test/java/io/github/wulkanowy/data/repositories/semester/SemesterRepositoryTest.kt b/app/src/test/java/io/github/wulkanowy/data/repositories/semester/SemesterRepositoryTest.kt
new file mode 100644
index 000000000..7856b9370
--- /dev/null
+++ b/app/src/test/java/io/github/wulkanowy/data/repositories/semester/SemesterRepositoryTest.kt
@@ -0,0 +1,74 @@
+package io.github.wulkanowy.data.repositories.semester
+
+import com.github.pwittchen.reactivenetwork.library.rx2.internet.observing.InternetObservingSettings
+import io.github.wulkanowy.data.ApiHelper
+import io.github.wulkanowy.data.db.entities.Semester
+import io.github.wulkanowy.data.db.entities.Student
+import io.github.wulkanowy.data.repositories.UnitTestInternetObservingStrategy
+import io.reactivex.Maybe
+import io.reactivex.Single
+import org.junit.Before
+import org.junit.Test
+import org.mockito.Mock
+import org.mockito.Mockito.doNothing
+import org.mockito.Mockito.doReturn
+import org.mockito.Mockito.verify
+import org.mockito.MockitoAnnotations
+
+class SemesterRepositoryTest {
+
+    @Mock
+    private lateinit var semesterRemote: SemesterRemote
+
+    @Mock
+    private lateinit var semesterLocal: SemesterLocal
+
+    @Mock
+    private lateinit var apiHelper: ApiHelper
+
+    @Mock
+    private lateinit var student: Student
+
+    private lateinit var semesterRepository: SemesterRepository
+
+    private val settings = InternetObservingSettings.builder()
+        .strategy(UnitTestInternetObservingStrategy())
+        .build()
+
+    @Before
+    fun initTest() {
+        MockitoAnnotations.initMocks(this)
+        semesterRepository = SemesterRepository(semesterRemote, semesterLocal, settings, apiHelper)
+    }
+
+    @Test
+    fun singleCurrentSemesterTest() {
+        val semesters = listOf(
+            createSemesterEntity(false),
+            createSemesterEntity(true)
+        )
+
+        doNothing().`when`(apiHelper).initApi(student)
+        doReturn(Maybe.empty<Semester>()).`when`(semesterLocal).getSemesters(student)
+        doReturn(Single.just(semesters)).`when`(semesterRemote).getSemesters(student)
+
+        semesterRepository.getSemesters(student).blockingGet()
+
+        verify(semesterLocal).deleteSemesters(emptyList())
+        verify(semesterLocal).saveSemesters(semesters)
+    }
+
+    @Test(expected = IllegalArgumentException::class)
+    fun twoCurrentSemesterTest() {
+        val semesters = listOf(
+            createSemesterEntity(true),
+            createSemesterEntity(true)
+        )
+
+        doNothing().`when`(apiHelper).initApi(student)
+        doReturn(Maybe.empty<Semester>()).`when`(semesterLocal).getSemesters(student)
+        doReturn(Single.just(semesters)).`when`(semesterRemote).getSemesters(student)
+
+        semesterRepository.getSemesters(student).blockingGet()
+    }
+}
diff --git a/app/src/test/java/io/github/wulkanowy/data/repositories/semester/TestSemesterEnityCreator.kt b/app/src/test/java/io/github/wulkanowy/data/repositories/semester/TestSemesterEnityCreator.kt
new file mode 100644
index 000000000..c3377ac51
--- /dev/null
+++ b/app/src/test/java/io/github/wulkanowy/data/repositories/semester/TestSemesterEnityCreator.kt
@@ -0,0 +1,16 @@
+package io.github.wulkanowy.data.repositories.semester
+
+import io.github.wulkanowy.data.db.entities.Semester
+
+fun createSemesterEntity(current: Boolean): Semester {
+    return Semester(
+        studentId = 0,
+        diaryId = 0,
+        semesterId = 0,
+        diaryName = "",
+        classId = 0,
+        isCurrent = current,
+        semesterName = 0,
+        unitId = 0
+    )
+}
diff --git a/app/src/test/java/io/github/wulkanowy/data/repositories/remote/StudentRemoteTest.kt b/app/src/test/java/io/github/wulkanowy/data/repositories/student/StudentRemoteTest.kt
similarity index 87%
rename from app/src/test/java/io/github/wulkanowy/data/repositories/remote/StudentRemoteTest.kt
rename to app/src/test/java/io/github/wulkanowy/data/repositories/student/StudentRemoteTest.kt
index 3a26836de..1244239e8 100644
--- a/app/src/test/java/io/github/wulkanowy/data/repositories/remote/StudentRemoteTest.kt
+++ b/app/src/test/java/io/github/wulkanowy/data/repositories/student/StudentRemoteTest.kt
@@ -1,8 +1,7 @@
-package io.github.wulkanowy.data.repositories.remote
+package io.github.wulkanowy.data.repositories.student
 
 import io.github.wulkanowy.api.Api
 import io.github.wulkanowy.api.register.Student
-import io.github.wulkanowy.data.repositories.student.StudentRemote
 import io.reactivex.Single
 import org.junit.Assert.assertEquals
 import org.junit.Before
diff --git a/app/src/test/java/io/github/wulkanowy/data/repositories/remote/TimetableRemoteTest.kt b/app/src/test/java/io/github/wulkanowy/data/repositories/timetable/TimetableRemoteTest.kt
similarity index 96%
rename from app/src/test/java/io/github/wulkanowy/data/repositories/remote/TimetableRemoteTest.kt
rename to app/src/test/java/io/github/wulkanowy/data/repositories/timetable/TimetableRemoteTest.kt
index 942b28ed9..4bb4091fb 100644
--- a/app/src/test/java/io/github/wulkanowy/data/repositories/remote/TimetableRemoteTest.kt
+++ b/app/src/test/java/io/github/wulkanowy/data/repositories/timetable/TimetableRemoteTest.kt
@@ -1,4 +1,4 @@
-package io.github.wulkanowy.data.repositories.remote
+package io.github.wulkanowy.data.repositories.timetable
 
 import io.github.wulkanowy.api.Api
 import io.github.wulkanowy.api.timetable.Timetable