test(utils): add tests for 'clamp' and 'getDecimalPrecision'

Author: arturbien

src/components/Select/Select.js

@@ -4,7 +4,7 @@ import propTypes from 'prop-types';
 import useControlledOrUncontrolled from '../common/hooks/useControlledOrUncontrolled';
 import useForkRef from '../common/hooks/useForkRef';
 
-import { clamp, areEqualValues } from '../common/utils';
+import { clamp } from '../common/utils';
 
 import {
   StyledDropdownButton,
@@ -30,10 +30,17 @@ const KEYS = {
   TAB: 'Tab'
 };
 
-export const getWrapper = variant =>
+function areEqualValues(a, b) {
+  if (typeof b === 'object' && b !== null) {
+    return a === b;
+  }
+  return String(a) === String(b);
+}
+
+const getWrapper = variant =>
   variant === 'flat' ? StyledFlatSelectWrapper : StyledSelectWrapper;
 
-export const getDisplayLabel = (selectedOption, formatDisplay) => {
+const getDisplayLabel = (selectedOption, formatDisplay) => {
   if (selectedOption) {
     if (formatDisplay) {
       return formatDisplay(selectedOption);
@@ -43,7 +50,7 @@ export const getDisplayLabel = (selectedOption, formatDisplay) => {
   return '';
 };
 
-export const getDefaultValue = (defaultValue, options) => {
+const getDefaultValue = (defaultValue, options) => {
   if (defaultValue) {
     return defaultValue;
   }

src/components/Slider/Slider.js

@@ -10,12 +10,16 @@ import {
   createDisabledTextStyles,
   createHatchedBackground
 } from '../common';
-import { clamp, percentToValue, roundValueToStep } from '../common/utils';
+import { clamp, roundValueToStep } from '../common/utils';
 import useControlledOrUncontrolled from '../common/hooks/useControlledOrUncontrolled';
 import useForkRef from '../common/hooks/useForkRef';
 import { useIsFocusVisible } from '../common/hooks/useIsFocusVisible';
 import Cutout from '../Cutout/Cutout';
 
+function percentToValue(percent, min, max) {
+  return (max - min) * percent + min;
+}
+
 function trackFinger(event, touchId) {
   if (touchId.current !== undefined && event.changedTouches) {
     for (let i = 0; i < event.changedTouches.length; i += 1) {

src/components/common/utils/index.js

@@ -1,19 +1,15 @@
 export const noOp = () => {};
 
 export function clamp(value, min, max) {
-  if (min !== null && value > max) {
+  if (max !== null && value > max) {
     return max;
   }
-  if (max !== null && value < min) {
+  if (min !== null && value < min) {
     return min;
   }
   return value;
 }
 
-export function percentToValue(percent, min, max) {
-  return (max - min) * percent + min;
-}
-
 // helper functions below are from Material UI (https://github.com/mui-org/material-ui)
 export function getDecimalPrecision(num) {
   if (Math.abs(num) < 1) {
@@ -33,10 +29,3 @@ export function roundValueToStep(value, step, min) {
   const nearest = Math.round((value - min) / step) * step + min;
   return Number(nearest.toFixed(getDecimalPrecision(step)));
 }
-
-export function areEqualValues(a, b) {
-  if (typeof b === 'object' && b !== null) {
-    return a === b;
-  }
-  return String(a) === String(b);
-}

src/components/common/utils/index.spec.js

@@ -0,0 +1,43 @@
+import { clamp, getDecimalPrecision, roundValueToStep } from './index';
+
+describe('clamp', () => {
+  it('should return passed value if its between min and max', () => {
+    expect(clamp(4, 3, 5)).toBe(4);
+  });
+
+  it('should return min if value is smaller than min', () => {
+    expect(clamp(2, 3, 5)).toBe(3);
+  });
+
+  it('should return max if value is bigger than max', () => {
+    expect(clamp(6, 3, 5)).toBe(5);
+  });
+
+  it('should accept null as min', () => {
+    expect(clamp(6, null, 5)).toBe(5);
+  });
+
+  it('should accept null as max', () => {
+    expect(clamp(1, 2, null)).toBe(2);
+  });
+});
+
+describe('getDecimalPrecision', () => {
+  it('should return 0 when passed a round number', () => {
+    expect(getDecimalPrecision(4)).toBe(0);
+  });
+
+  it('should return correct decimal precision', () => {
+    expect(getDecimalPrecision(1.233)).toBe(3);
+  });
+});
+
+describe('roundValueToStep', () => {
+  it('should be able to round down', () => {
+    expect(roundValueToStep(4, 3, 0)).toBe(3);
+  });
+
+  it('should be able to round up', () => {
+    expect(roundValueToStep(5, 3, 0)).toBe(6);
+  });
+});