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calculate operational and embodied emissions per segment
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‎src/constants/index.js‎

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@@ -24,6 +24,16 @@ const FIRST_TIME_VIEWING_PERCENTAGE = 0.75;
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const RETURNING_VISITOR_PERCENTAGE = 0.25;
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const PERCENTAGE_OF_DATA_LOADED_ON_SUBSEQUENT_LOAD = 0.02;
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const SWDV4 = {
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OPERATIONAL_KWH_PER_GB_DATACENTER: 0.055,
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OPERATIONAL_KWH_PER_GB_NETWORK: 0.059,
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OPERATIONAL_KWH_PER_GB_DEVICE: 0.08,
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EMBODIED_KWH_PER_GB_DATACENTER: 0.012,
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EMBODIED_KWH_PER_GB_NETWORK: 0.013,
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EMBODIED_KWH_PER_GB_DEVICE: 0.081,
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GLOBAL_GRID_INTENSITY: 494,
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};
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export {
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fileSize,
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KWH_PER_GB,
@@ -36,4 +46,5 @@ export {
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FIRST_TIME_VIEWING_PERCENTAGE,
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RETURNING_VISITOR_PERCENTAGE,
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PERCENTAGE_OF_DATA_LOADED_ON_SUBSEQUENT_LOAD,
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SWDV4,
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};

‎src/sustainable-web-design-v4.js‎

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"use strict";
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/**
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* Sustainable Web Design version 4
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*
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* Updated calculations and figures from
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* https://sustainablewebdesign.org/estimating-digital-emissions/
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*
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*/
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import { fileSize, SWDV4 } from "./constants/index.js";
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import { formatNumber } from "./helpers/index.js";
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const {
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OPERATIONAL_KWH_PER_GB_DATACENTER,
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OPERATIONAL_KWH_PER_GB_NETWORK,
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OPERATIONAL_KWH_PER_GB_DEVICE,
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EMBODIED_KWH_PER_GB_DATACENTER,
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EMBODIED_KWH_PER_GB_NETWORK,
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EMBODIED_KWH_PER_GB_DEVICE,
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GLOBAL_GRID_INTENSITY,
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} = SWDV4;
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class SustainableWebDesign {
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constructor(options) {
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this.options = options;
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}
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/**
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* Calculate the operational energy of data transfer for each system segment
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*
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* @param {number} bytes
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* @returns {object}
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*/
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operationalEnergyPerSegment(bytes) {
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const transferedBytesToGb = bytes / fileSize.GIGABYTE;
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const dataCenter = transferedBytesToGb * OPERATIONAL_KWH_PER_GB_DATACENTER;
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const network = transferedBytesToGb * OPERATIONAL_KWH_PER_GB_NETWORK;
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const device = transferedBytesToGb * OPERATIONAL_KWH_PER_GB_DEVICE;
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return {
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dataCenter,
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network,
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device,
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};
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}
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/**
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* Calculate the operational emissions of data transfer for each system segment
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*
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* @param {number} bytes
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* @param {object} options
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* @returns {object}
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*/
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operationalEmissions(bytes, options = {}) {
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const { dataCenter, network, device } =
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this.operationalEnergyPerSegment(bytes);
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let dataCenterGridIntensity = GLOBAL_GRID_INTENSITY;
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let networkGridIntensity = GLOBAL_GRID_INTENSITY;
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let deviceGridIntensity = GLOBAL_GRID_INTENSITY;
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if (options?.gridIntensity) {
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const { device, network, dataCenter } = options.gridIntensity;
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if (device?.value || device?.value === 0) {
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deviceGridIntensity = device.value;
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}
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if (network?.value || network?.value === 0) {
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networkGridIntensity = network.value;
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}
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if (dataCenter?.value || dataCenter?.value === 0) {
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dataCenterGridIntensity = dataCenter.value;
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}
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}
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const dataCenterEmissions = dataCenter * dataCenterGridIntensity;
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const networkEmissions = network * networkGridIntensity;
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const deviceEmissions = device * deviceGridIntensity;
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return {
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dataCenter: dataCenterEmissions,
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network: networkEmissions,
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device: deviceEmissions,
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};
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}
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/**
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* Calculate the embodied energy of data transfer for each system segment
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*
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* @param {number} bytes
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* @returns {object}
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*/
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embodiedEnergyPerSegment(bytes) {
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const transferedBytesToGb = bytes / fileSize.GIGABYTE;
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const dataCenter = transferedBytesToGb * EMBODIED_KWH_PER_GB_DATACENTER;
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const network = transferedBytesToGb * EMBODIED_KWH_PER_GB_NETWORK;
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const device = transferedBytesToGb * EMBODIED_KWH_PER_GB_DEVICE;
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return {
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dataCenter,
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network,
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device,
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};
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}
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/**
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* Calculate the embodied emissions of data transfer for each system segment
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*
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* @param {number} bytes
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* @returns {object}
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*/
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embodiedEmissions(bytes) {
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const { dataCenter, network, device } =
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this.embodiedEnergyPerSegment(bytes);
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const dataCenterGridIntensity = GLOBAL_GRID_INTENSITY;
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const networkGridIntensity = GLOBAL_GRID_INTENSITY;
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const deviceGridIntensity = GLOBAL_GRID_INTENSITY;
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// NOTE: Per the guidance in the SWDM v4, the grid intensity values for embodied emissions are fixed to the global grid intensity.
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const dataCenterEmissions = dataCenter * dataCenterGridIntensity;
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const networkEmissions = network * networkGridIntensity;
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const deviceEmissions = device * deviceGridIntensity;
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return {
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dataCenter: dataCenterEmissions,
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network: networkEmissions,
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device: deviceEmissions,
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};
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}
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}
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export { SustainableWebDesign };
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export default SustainableWebDesign;

‎src/sustainable-web-design-v4.test.js‎

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import SustainableWebDesign from "./sustainable-web-design-v4.js";
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import { MILLION, SWDV4 } from "./constants/test-constants.js";
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describe("sustainable web design model version 4", () => {
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const swd = new SustainableWebDesign();
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describe("operational emissions", () => {
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it("returns the expected emissions for 1GB data transfer", () => {
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const result = swd.operationalEmissions(1000000000);
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expect(result).toEqual(
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expect.objectContaining({
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dataCenter: expect.any(Number),
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network: expect.any(Number),
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device: expect.any(Number),
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})
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);
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expect(result.dataCenter).toBeCloseTo(27.17, 3);
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expect(result.network).toBeCloseTo(29.146, 3);
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expect(result.device).toBeCloseTo(39.52, 3);
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});
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it("returns the expected emissions for 0bytes data transfer", () => {
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const result = swd.operationalEmissions(0);
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expect(result).toEqual(
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expect.objectContaining({
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dataCenter: expect.any(Number),
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network: expect.any(Number),
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device: expect.any(Number),
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})
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);
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expect(result.dataCenter).toBeCloseTo(0, 3);
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expect(result.network).toBeCloseTo(0, 3);
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expect(result.device).toBeCloseTo(0, 3);
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});
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if (
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("returns the expected emissions for 1GB data transfer with custom grid intensities",
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() => {
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const result = swd.operationalEmissions(1000000000, {
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gridIntensity: {
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dataCenter: { value: 100 },
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network: { value: 200 },
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device: { value: 300 },
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},
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});
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expect(result).toEqual(
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expect.objectContaining({
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dataCenter: expect.any(Number),
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network: expect.any(Number),
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device: expect.any(Number),
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})
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);
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expect(result.dataCenter).toBeCloseTo(5.5, 3);
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expect(result.network).toBeCloseTo(11.8, 3);
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expect(result.device).toBeCloseTo(24, 3);
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})
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);
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});
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describe("embodied emissions", () => {
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it("returns the expected emissions for 1GB data transfer", () => {
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const result = swd.embodiedEmissions(1000000000);
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expect(result).toEqual(
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expect.objectContaining({
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dataCenter: expect.any(Number),
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network: expect.any(Number),
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device: expect.any(Number),
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})
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);
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expect(result.dataCenter).toBeCloseTo(5.928, 3);
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expect(result.network).toBeCloseTo(6.422, 3);
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expect(result.device).toBeCloseTo(40.014, 3);
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});
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it("returns the expected emissions for 0bytes data transfer", () => {
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const result = swd.embodiedEmissions(0);
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expect(result).toEqual(
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expect.objectContaining({
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dataCenter: expect.any(Number),
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network: expect.any(Number),
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device: expect.any(Number),
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})
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);
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expect(result.dataCenter).toBeCloseTo(0, 3);
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expect(result.network).toBeCloseTo(0, 3);
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expect(result.device).toBeCloseTo(0, 3);
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});
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});
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});

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