add tests for util functions

Author: jscottsmith

__tests__/clamp.test.js

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+import clamp from 'utils/clamp.js';
+
+const max = 100;
+const min = 10;
+
+test('Clamps a value within a range', () => {
+    expect(clamp(50, min, max))
+        .toBe(50);
+
+    expect(clamp(110, min, max))
+        .toBe(max);
+
+    expect(clamp(0, min, max))
+        .toBe(min);
+});

__tests__/getParallaxOffsets.test.js

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+import getParallaxOffsets from 'utils/getParallaxOffsets.js';
+import { parseValueAndUnit, scaleBetween } from 'utils';
+
+const offset = {
+    xMin: parseValueAndUnit('-100px'),
+    xMax: parseValueAndUnit('40px'),
+    yMin: parseValueAndUnit('-80%'),
+    yMax: parseValueAndUnit('50%'),
+};
+
+const percentMoved = 44;
+
+test('Gets offsets based on percent in view', () => {
+    expect(getParallaxOffsets(offset, percentMoved, false)).toEqual({
+        x: {
+            value: scaleBetween(percentMoved, offset.xMax.value, offset.xMin.value, 0, 100),
+            unit: offset.xMax.unit,
+        },
+        y: {
+            value: scaleBetween(percentMoved, offset.yMax.value, offset.yMin.value, 0, 100),
+            unit: offset.yMax.unit,
+        },
+    });
+
+    expect(getParallaxOffsets(offset, percentMoved, true)).toEqual({
+        x: {
+            value: scaleBetween(percentMoved, offset.xMin.value, offset.xMax.value, 0, 100),
+            unit: offset.xMax.unit,
+        },
+        y: {
+            value: scaleBetween(percentMoved, offset.yMin.value, offset.yMax.value, 0, 100),
+            unit: offset.yMax.unit,
+        },
+    });
+});

__tests__/parseValueAndUnit.test.js

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+import parseValueAndUnit from 'utils/parseValueAndUnit';
+
+test('Parse a string to get the value and unit in either pixels or percent', () => {
+    expect(parseValueAndUnit('5px'))
+        .toEqual({ unit: 'px', value: 5 });
+    expect(parseValueAndUnit('52%'))
+        .toEqual({ unit: '%', value: 52 });
+    expect(parseValueAndUnit(13.333))
+        .toEqual({ unit: null, value: 13.333 });
+    expect(parseValueAndUnit('75.8%'))
+        .toEqual({ unit: '%', value: 75 });
+    expect(parseValueAndUnit('23.1px'))
+        .toEqual({ unit: 'px', value: 23 });
+    expect(() => parseValueAndUnit(false))
+        .toThrow();
+});

__tests__/scaleBetween.test.js

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+import scaleBetween from 'utils/scaleBetween.js';
+
+const oldMin = 0;
+const oldMax = 1;
+
+const newMin = 0;
+const newMax = 100;
+
+test('Scales a value from a given range to a new range', () => {
+    expect(scaleBetween(0.4, newMin, newMax, oldMin, oldMax))
+        .toBe(40);
+    expect(scaleBetween(0.1, newMin, newMax, oldMin, oldMax))
+        .toBe(10);
+    expect(scaleBetween(0.3, newMin, newMax, oldMin, oldMax))
+        .toBe(30);
+    expect(scaleBetween(0.333, newMin, newMax, oldMin, oldMax))
+        .toBeCloseTo(33.3);
+});