Test MigrationService data directory version detection

- Test with data directory before MigrationService was introduced
- Test with invalid data directory version
- Test with valid data directory version

application/src/test/java/bisq/application/migration/MigrationServiceTests.java

@@ -0,0 +1,43 @@
+package bisq.application.migration;
+
+import bisq.common.platform.InvalidVersionException;
+import bisq.common.platform.Version;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+public class MigrationServiceTests {
+    @Test
+    void getDataDirVersionBeforeMigrationServiceIntroduced(@TempDir Path dataDir) {
+        MigrationService migrationService = new MigrationService(dataDir);
+        Version dataDirVersion = migrationService.getDataDirVersion();
+        assertThat(dataDirVersion)
+                .isEqualTo(MigrationService.VERSION_BEFORE_MIGRATION_SERVICE_INTRODUCED);
+    }
+
+    @Test
+    void getDataDirInvalidVersion(@TempDir Path dataDir) throws IOException {
+        Path versionFilePath = dataDir.resolve("version");
+        Files.writeString(versionFilePath, "2.1-alpha");
+
+        MigrationService migrationService = new MigrationService(dataDir);
+        assertThrows(InvalidVersionException.class, migrationService::getDataDirVersion);
+    }
+
+    @Test
+    void getDataDirVersion(@TempDir Path dataDir) throws IOException {
+        Path versionFilePath = dataDir.resolve("version");
+        Files.writeString(versionFilePath, "2.1.34");
+
+        MigrationService migrationService = new MigrationService(dataDir);
+        Version dataDirVersion = migrationService.getDataDirVersion();
+        assertThat(dataDirVersion)
+                .isEqualTo(new Version("2.1.34"));
+    }
+}