add line graph, associated changes to utils/config/styles & test

test/component/line-graph.test.tsx

@@ -0,0 +1,21 @@
+import React from 'react';
+import { render } from '@testing-library/react-native';
+import LineGraph from '../../component/charts/line-graph/line-graph';
+import { line_chart_two_y_data } from '../../mock/charts/mock-data';
+
+describe('LineGraph Component Tests', () => {
+
+  it('renders correctly with data', () => {
+    const { getByTestId } = render(<LineGraph data={line_chart_two_y_data} testID='1'/>);
+    expect(getByTestId(`line-graph-1`)).toBeTruthy();
+
+  });
+
+  it('does not render without data', () => {
+    // Have to ts-ignore to test null data conditions
+    // @ts-ignore
+    const { queryByTestId } = render(<LineGraph testID='2'/>);
+    expect(queryByTestId(`line-graph-2`)).toBeNull();
+  });
+
+});