fix unit tests. add conversation model and add unit tests to it.

components/__tests__/ThemedText-test.tsx

@@ -1,10 +0,0 @@
-import * as React from 'react';
-import renderer from 'react-test-renderer';
-
-import { ThemedText } from '../ThemedText';
-
-it(`renders correctly`, () => {
-  const tree = renderer.create(<ThemedText>Snapshot test!</ThemedText>).toJSON();
-
-  expect(tree).toMatchSnapshot();
-});

components/__tests__/__snapshots__/ThemedText-test.tsx.snap

@@ -1,24 +0,0 @@
-// Jest Snapshot v1, https://goo.gl/fbAQLP
-
-exports[`renders correctly 1`] = `
-<Text
-  style={
-    [
-      {
-        "color": "#11181C",
-      },
-      {
-        "fontSize": 16,
-        "lineHeight": 24,
-      },
-      undefined,
-      undefined,
-      undefined,
-      undefined,
-      undefined,
-    ]
-  }
->
-  Snapshot test!
-</Text>
-`;