Add a CacheStore module.

libraries/cachestore/test/build.gradle.kts

@@ -0,0 +1,17 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+plugins {
+    id("io.element.android-library")
+}
+
+android {
+    namespace = "io.element.android.libraries.cachestore.test"
+}
+
+dependencies {
+    implementation(projects.libraries.cachestore.api)
+}

libraries/cachestore/test/src/main/kotlin/io/element/android/libraries/sessionstorage/test/CacheData.kt

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.sessionstorage.test
+
+import io.element.android.libraries.cachestore.api.CacheData
+
+fun aCacheData(
+    value: String = "aValue",
+    updatedAt: Long = 0,
+) = CacheData(
+    value = value,
+    updatedAt = updatedAt,
+)

libraries/cachestore/test/src/main/kotlin/io/element/android/libraries/sessionstorage/test/InMemoryCacheStore.kt

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.sessionstorage.test
+
+import io.element.android.libraries.cachestore.api.CacheData
+import io.element.android.libraries.cachestore.api.CacheStore
+
+class InMemoryCacheStore(
+    initialData: Map<String, CacheData> = emptyMap(),
+) : CacheStore {
+    val dataMap = initialData.toMutableMap()
+
+    override suspend fun storeData(key: String, data: CacheData) {
+        dataMap[key] = data
+    }
+
+    override suspend fun getData(key: String): CacheData? {
+        return dataMap[key]
+    }
+
+    override suspend fun deleteData(key: String) {
+        dataMap.remove(key)
+    }
+}