diff --git a/app/attachments.js b/app/attachments.js
new file mode 100644
index 000000000000..99a67fda993e
--- /dev/null
+++ b/app/attachments.js
@@ -0,0 +1,84 @@
+const crypto = require('crypto');
+const fse = require('fs-extra');
+const isArrayBuffer = require('lodash/isArrayBuffer');
+const isString = require('lodash/isString');
+const path = require('path');
+const toArrayBuffer = require('to-arraybuffer');
+
+
+const PATH = 'attachments';
+
+
+//      getPath :: AbsolutePath -> AbsolutePath
+exports.getPath = (userDataPath) => {
+  if (!isString(userDataPath)) {
+    throw new TypeError('`userDataPath` must be a string');
+  }
+  return path.join(userDataPath, PATH);
+};
+
+//      ensureDirectory :: AbsolutePath -> IO Unit
+exports.ensureDirectory = async (userDataPath) => {
+  if (!isString(userDataPath)) {
+    throw new TypeError('`userDataPath` must be a string');
+  }
+  await fse.ensureDir(exports.getPath(userDataPath));
+};
+
+//      readData :: AttachmentsPath ->
+//                  RelativePath ->
+//                  IO (Promise ArrayBuffer)
+exports.readData = (root) => {
+  if (!isString(root)) {
+    throw new TypeError('`root` must be a path');
+  }
+
+  return async (relativePath) => {
+    if (!isString(relativePath)) {
+      throw new TypeError('`relativePath` must be a string');
+    }
+
+    const absolutePath = path.join(root, relativePath);
+    const buffer = await fse.readFile(absolutePath);
+    return toArrayBuffer(buffer);
+  };
+};
+
+//      writeData :: AttachmentsPath ->
+//                   ArrayBuffer ->
+//                   IO (Promise RelativePath)
+exports.writeData = (root) => {
+  if (!isString(root)) {
+    throw new TypeError('`root` must be a path');
+  }
+
+  return async (arrayBuffer) => {
+    if (!isArrayBuffer(arrayBuffer)) {
+      throw new TypeError('`arrayBuffer` must be an array buffer');
+    }
+
+    const buffer = Buffer.from(arrayBuffer);
+    const name = exports.createName();
+    const relativePath = exports.getRelativePath(name);
+    const absolutePath = path.join(root, relativePath);
+    await fse.ensureFile(absolutePath);
+    await fse.writeFile(absolutePath, buffer);
+    return relativePath;
+  };
+};
+
+//      createName :: Unit -> IO String
+exports.createName = () => {
+  const buffer = crypto.randomBytes(32);
+  return buffer.toString('hex');
+};
+
+//      getRelativePath :: String -> IO Path
+exports.getRelativePath = (name) => {
+  if (!isString(name)) {
+    throw new TypeError('`name` must be a string');
+  }
+
+  const prefix = name.slice(0, 2);
+  return path.join(prefix, name);
+};
diff --git a/app/types/attachment/write_attachment_data.js b/app/types/attachment/write_attachment_data.js
deleted file mode 100644
index 7a595e94f948..000000000000
--- a/app/types/attachment/write_attachment_data.js
+++ /dev/null
@@ -1,41 +0,0 @@
-const crypto = require('crypto');
-const fse = require('fs-extra');
-const isArrayBuffer = require('lodash/isArrayBuffer');
-const isString = require('lodash/isString');
-const path = require('path');
-
-
-//      _writeAttachmentData :: AttachmentsPath ->
-//                              ArrayBuffer ->
-//                              IO (Promise Path)
-exports.writeAttachmentData = (root) => {
-  if (!isString(root)) {
-    throw new TypeError('`root` must be a path');
-  }
-
-  return async (arrayBuffer) => {
-    if (!isArrayBuffer(arrayBuffer)) {
-      throw new TypeError('`arrayBuffer` must be an array buffer');
-    }
-
-    const buffer = Buffer.from(arrayBuffer);
-    const relativePath = exports._getAttachmentPath();
-    const absolutePath = path.join(root, relativePath);
-    await fse.ensureFile(absolutePath);
-    await fse.writeFile(absolutePath, buffer);
-    return relativePath;
-  };
-};
-
-//      _getAttachmentName :: Unit -> IO String
-exports._getAttachmentName = () => {
-  const buffer = crypto.randomBytes(32);
-  return buffer.toString('hex');
-};
-
-//      _getAttachmentPath :: Unit -> IO Path
-exports._getAttachmentPath = () => {
-  const name = exports._getAttachmentName();
-  const prefix = name.slice(0, 2);
-  return path.join(prefix, name);
-};
diff --git a/preload.js b/preload.js
index f99d51b54756..c2d3d1a33c29 100644
--- a/preload.js
+++ b/preload.js
@@ -108,6 +108,10 @@
   window.autoOrientImage = autoOrientImage;
 
   // ES2015+ modules
+  const attachmentsPath = Attachments.getPath(app.getPath('userData'));
+  const readAttachmentData = Attachments.readData(attachmentsPath);
+  const writeAttachmentData = Attachments.writeData(attachmentsPath);
+
   window.Signal = window.Signal || {};
   window.Signal.Logs = require('./js/modules/logs');
   window.Signal.OS = require('./js/modules/os');
@@ -115,11 +119,10 @@
   window.Signal.Crypto = require('./js/modules/crypto');
 
   window.Signal.Migrations = window.Signal.Migrations || {};
-  const attachmentsPath = Attachments.getPath(app.getPath('userData'));
-  const { writeAttachmentData } = require('./app/types/attachment/write_attachment_data');
   // Injected context functions to keep `Message` agnostic from Electron:
   window.Signal.Migrations.context = {
-    writeAttachmentData: writeAttachmentData(attachmentsPath),
+    readAttachmentData,
+    writeAttachmentData,
   };
   window.Signal.Migrations.V17 = require('./js/modules/migrations/17');
 
diff --git a/test/app/attachments_test.js b/test/app/attachments_test.js
new file mode 100644
index 000000000000..a22d4f32cbed
--- /dev/null
+++ b/test/app/attachments_test.js
@@ -0,0 +1,53 @@
+const fse = require('fs-extra');
+const isEqual = require('lodash/isEqual');
+const path = require('path');
+const stringToArrayBuffer = require('string-to-arraybuffer');
+const tmp = require('tmp');
+const { assert } = require('chai');
+
+const Attachments = require('../../app/attachments');
+
+
+const PREFIX_LENGTH = 2;
+const NUM_SEPARATORS = 1;
+const NAME_LENGTH = 64;
+const PATH_LENGTH = PREFIX_LENGTH + NUM_SEPARATORS + NAME_LENGTH;
+
+describe('Attachments', () => {
+  describe('writeData', () => {
+    let TEMPORARY_DIRECTORY = null;
+    before(() => {
+      TEMPORARY_DIRECTORY = tmp.dirSync().name;
+    });
+
+    after(async () => {
+      await fse.remove(TEMPORARY_DIRECTORY);
+    });
+
+    it('should write file to disk and return path', async () => {
+      const input = stringToArrayBuffer('test string');
+      const tempDirectory = path.join(TEMPORARY_DIRECTORY, 'Attachments_writeData');
+
+      const outputPath = await Attachments.writeData(tempDirectory)(input);
+      const output = await fse.readFile(path.join(tempDirectory, outputPath));
+
+      assert.lengthOf(outputPath, PATH_LENGTH);
+
+      const inputBuffer = Buffer.from(input);
+      assert.isTrue(isEqual(inputBuffer, output));
+    });
+
+    describe('createName', () => {
+      it('should return random file name with correct length', () => {
+        assert.lengthOf(Attachments.createName(), NAME_LENGTH);
+      });
+    });
+
+    describe('getRelativePath', () => {
+      it('should return correct path', () => {
+        const name = '608ce3bc536edbf7637a6aeb6040bdfec49349140c0dd43e97c7ce263b15ff7e';
+        assert.lengthOf(Attachments.getRelativePath(name), PATH_LENGTH);
+      });
+    });
+  });
+});
diff --git a/test/app/types/attachment/write_attachment_data_test.js b/test/app/types/attachment/write_attachment_data_test.js
deleted file mode 100644
index 1e00664e1a99..000000000000
--- a/test/app/types/attachment/write_attachment_data_test.js
+++ /dev/null
@@ -1,54 +0,0 @@
-const fse = require('fs-extra');
-const isEqual = require('lodash/isEqual');
-const path = require('path');
-const stringToArrayBuffer = require('string-to-arraybuffer');
-const tmp = require('tmp');
-const { assert } = require('chai');
-
-const {
-  writeAttachmentData,
-  _getAttachmentName,
-  _getAttachmentPath,
-} = require('../../../../app/types/attachment/write_attachment_data');
-
-
-const PREFIX_LENGTH = 2;
-const NUM_SEPARATORS = 1;
-const NAME_LENGTH = 64;
-const PATH_LENGTH = PREFIX_LENGTH + NUM_SEPARATORS + NAME_LENGTH;
-
-describe('writeAttachmentData', () => {
-  let TEMPORARY_DIRECTORY = null;
-  before(() => {
-    TEMPORARY_DIRECTORY = tmp.dirSync().name;
-  });
-
-  after(async () => {
-    await fse.remove(TEMPORARY_DIRECTORY);
-  });
-
-  it('should write file to disk and return path', async () => {
-    const input = stringToArrayBuffer('test string');
-    const tempDirectory = path.join(TEMPORARY_DIRECTORY, 'writeAttachmentData');
-
-    const outputPath = await writeAttachmentData(tempDirectory)(input);
-    const output = await fse.readFile(path.join(tempDirectory, outputPath));
-
-    assert.lengthOf(outputPath, PATH_LENGTH);
-
-    const inputBuffer = Buffer.from(input);
-    assert.isTrue(isEqual(inputBuffer, output));
-  });
-
-  describe('_getAttachmentName', () => {
-    it('should return random file name with correct length', () => {
-      assert.lengthOf(_getAttachmentName(), NAME_LENGTH);
-    });
-  });
-
-  describe('_getAttachmentPath', () => {
-    it('should return correct path', () => {
-      assert.lengthOf(_getAttachmentPath(), PATH_LENGTH);
-    });
-  });
-});