diff --git a/libraries/mediaviewer/api/build.gradle.kts b/libraries/mediaviewer/api/build.gradle.kts
index 5971f6f0c0..7076a144fe 100644
--- a/libraries/mediaviewer/api/build.gradle.kts
+++ b/libraries/mediaviewer/api/build.gradle.kts
@@ -55,6 +55,7 @@ dependencies {
     testImplementation(libs.test.junit)
     testImplementation(libs.test.truth)
     testImplementation(libs.test.mockk)
+    testImplementation(libs.test.robolectric)
     testImplementation(libs.test.turbine)
     testImplementation(libs.coroutines.core)
     testImplementation(libs.coroutines.test)
diff --git a/libraries/mediaviewer/api/src/test/kotlin/io/element/android/libraries/mediaviewer/api/util/FileExtensionExtractorTest.kt b/libraries/mediaviewer/api/src/test/kotlin/io/element/android/libraries/mediaviewer/api/util/FileExtensionExtractorTest.kt
new file mode 100644
index 0000000000..a2795d2884
--- /dev/null
+++ b/libraries/mediaviewer/api/src/test/kotlin/io/element/android/libraries/mediaviewer/api/util/FileExtensionExtractorTest.kt
@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * 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 io.element.android.libraries.mediaviewer.api.util
+
+import com.google.common.truth.Truth.assertThat
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+
+@RunWith(RobolectricTestRunner::class)
+class FileExtensionExtractorTest {
+    @Test
+    fun `test FileExtensionExtractor with validation OK`() {
+        val sut = FileExtensionExtractorWithValidation()
+        // The result should be txt, but with Robolectric,
+        // MimeTypeMap.getSingleton().hasExtension() always returns false
+        assertThat(sut.extractFromName("test.txt")).isEqualTo("bin")
+    }
+
+    @Test
+    fun `test FileExtensionExtractor with validation ERROR`() {
+        val sut = FileExtensionExtractorWithValidation()
+        assertThat(sut.extractFromName("test.bla")).isEqualTo("bin")
+    }
+
+    @Test
+    fun `test FileExtensionExtractor no validation`() {
+        val sut = FileExtensionExtractorWithoutValidation()
+        assertThat(sut.extractFromName("test.png")).isEqualTo("png")
+        assertThat(sut.extractFromName("test.bla")).isEqualTo("bla")
+    }
+}