added test

packages/xy-chart/test/utils/chartUtils.test.js

@@ -1,6 +1,12 @@
 import React from 'react';
+import { scaleLinear, scaleBand } from '@vx/scale';
 
-import { callOrValue, componentName } from '../../src/utils/chartUtils';
+import {
+  callOrValue,
+  componentName,
+  scaleInvert,
+  getDomainFromExtent,
+} from '../../src/utils/chartUtils';
 
 describe('callOrValue', () => {
   it('should return non-functions', () => {
@@ -41,3 +47,53 @@ describe('componentName', () => {
     expect(componentName(SFC)).toBe('');
   });
 });
+
+describe('scaleInvert', () => {
+  it('should work correct with non-band or no-ordinal Scale', () => {
+    const linearScale = scaleLinear({
+      range: [0, 1000],
+      domain: [0, 100],
+    });
+    expect(linearScale.invert(10)).toEqual(scaleInvert(linearScale, 10));
+  });
+
+  it('should work correct with band or ordinal Scales', () => {
+    const domain = [1, 2, 3, 4, 5];
+    const bandScale = scaleBand({
+      rangeRound: [0, 100],
+      domain,
+    });
+    expect(scaleInvert(bandScale, 30)).toEqual(1);
+    expect(scaleInvert(bandScale, 90)).toEqual(4);
+  });
+});
+
+describe('getDomainFromExtent', () => {
+  it('should work correct with non-band or no-ordinal Scale', () => {
+    const linearScale = scaleLinear({
+      range: [0, 1000],
+      domain: [0, 100],
+    });
+    const delta = 2;
+    const start = 10;
+    const end = 20;
+    const domain = getDomainFromExtent(linearScale, start, end, delta);
+    expect(domain.start).toEqual(linearScale.invert(start - 2));
+    expect(domain.end).toEqual(linearScale.invert(end + 2));
+  });
+
+  it('should work correct with band or ordinal Scales', () => {
+    const domain = ['test1', 'test5', 'test3', 'test3', 'test4'];
+    const bandScale = scaleBand({
+      rangeRound: [0, 100],
+      domain,
+    });
+    const delta = 2;
+    const start = 10;
+    const end = 30;
+    const selectedDomain = getDomainFromExtent(bandScale, start, end, delta);
+    expect(selectedDomain.values).toHaveLength(2);
+    expect(selectedDomain.values[0]).toEqual('test1');
+    expect(selectedDomain.values[1]).toEqual('test5');
+  });
+});