crypto migration tests

.gitattributes

@@ -1 +1,2 @@
 **/snapshots/**/*.png filter=lfs diff=lfs merge=lfs -text
+**/src/androidTest/assets/*.realm filter=lfs diff=lfs merge=lfs -text

changelog.d/7645.misc

@@ -0,0 +1 @@
+Crypto database migration tests

docs/database_migration_test.md

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+<!--- TOC -->
+
+* [Testing database migration](#testing-database-migration)
+  * [Creating a reference database](#creating-a-reference-database)
+  * [Testing](#testing)
+
+<!--- END -->
+
+## Testing database migration
+
+### Creating a reference database
+
+Databases are encrypted, the key to decrypt is needed to setup the test.
+A special build property must be enabled to extract it. 
+
+Set `vector.debugPrivateData=true` in `~/.gradle/gradle.properties` (to avoid committing by mistake)
+
+Launch the app in your emulator, login and use the app to fill up the database.
+
+Save the key for the tested database
+```
+RealmKeysUtils  W  Database key for alias `session_db_fe9f212a611ccf6dea1141777065ed0a`: 935a6dfa0b0fc5cce1414194ed190....
+RealmKeysUtils  W  Database key for alias `crypto_module_fe9f212a611ccf6dea1141777065ed0a`: 7b9a21a8a311e85d75b069a343.....
+```
+
+
+Use the [Device File Explorer](https://developer.android.com/studio/debug/device-file-explorer) to extrat the database file from the emulator.
+
+Go to `data/data/im.vector.app.debug/files/<hash>/`
+Pick the database you want to test (name can be found in SessionRealmConfigurationFactory):
+ - crypto_store.realm for crypto
+ - disk_store.realm for session
+ - etc... 
+
+Download the file on your disk
+
+### Testing
+
+Copy the file in `src/AndroidTest/assets`
+
+see `CryptoSanityMigrationTest` or `RealmSessionStoreMigration43Test` for sample tests.
+
+There are already some databases in the assets folder.
+The existing test will properly detect schema changes, and fail with such errors if a migration is missing:
+
+```
+io.realm.exceptions.RealmMigrationNeededException: Migration is required due to the following errors:
+- Property 'CryptoMetadataEntity.foo' has been added.
+```
+
+If you want to test properly more complex database migration (dynamic transforms) ensure that the database contains
+the entity you want to migrate.
+
+You can explore the database with [realm studio](https://www.mongodb.com/docs/realm/studio/) if needed.
+

matrix-sdk-android/src/androidTest/java/org/matrix/android/sdk/internal/database/CryptoSanityMigrationTest.kt

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+/*
+ * Copyright 2022 The Matrix.org Foundation C.I.C.
+ *
+ * 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
+ *
+ *     http://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 org.matrix.android.sdk.internal.database
+
+import android.content.Context
+import androidx.test.platform.app.InstrumentationRegistry
+import io.realm.Realm
+import org.junit.After
+import org.junit.Before
+import org.junit.Rule
+import org.junit.Test
+import org.matrix.android.sdk.internal.crypto.store.db.RealmCryptoStoreMigration
+import org.matrix.android.sdk.internal.crypto.store.db.RealmCryptoStoreModule
+import org.matrix.android.sdk.internal.util.time.Clock
+
+class CryptoSanityMigrationTest {
+    @get:Rule val configurationFactory = TestRealmConfigurationFactory()
+
+    lateinit var context: Context
+    var realm: Realm? = null
+
+    @Before
+    fun setUp() {
+        context = InstrumentationRegistry.getInstrumentation().context
+    }
+
+    @After
+    fun tearDown() {
+        realm?.close()
+    }
+
+    @Test
+    fun cryptoDatabaseShouldMigrateGracefully() {
+        val realmName = "crypto_store_20.realm"
+        val migration = RealmCryptoStoreMigration(object : Clock {
+            override fun epochMillis(): Long {
+                return 0L
+            }
+        })
+        val realmConfiguration = configurationFactory.createConfiguration(
+                realmName,
+                "7b9a21a8a311e85d75b069a343c23fc952fc3fec5e0c83ecfa13f24b787479c487c3ed587db3dd1f5805d52041fc0ac246516e94b27ffa699ff928622e621aca",
+                RealmCryptoStoreModule(),
+                migration.schemaVersion,
+                migration
+        )
+        configurationFactory.copyRealmFromAssets(context, realmName, realmName)
+
+        realm = Realm.getInstance(realmConfiguration)
+    }
+}