Add tests and optimization/compression for rendered metrics

tests/metrics.mjs

@@ -0,0 +1,26 @@
+//Imports
+  import path from "path"
+  import fs from "fs"
+  import metrics from "../src/metrics.mjs"
+  import octokit from "@octokit/graphql"
+  import OctokitRest from "@octokit/rest"
+  import libxmljs from "libxmljs"
+
+//Die on unhandled rejections
+  process.on("unhandledRejection", error => { throw error })
+
+//Load GitHub handlers
+  const token = process.argv.slice(2)[0] ?? ""
+  const graphql = octokit.graphql.defaults({headers:{authorization: `token ${token}`}})
+  const rest = new OctokitRest.Octokit({auth:token})
+
+//Load svg template, style and query
+  const [template, style, query] = await Promise.all(["template.svg", "style.css", "query.graphql"].map(async file => `${await fs.promises.readFile(path.join("src", file))}`))
+
+//Compute render
+  const rendered = await metrics({login:"lowlighter", q:{}}, {template, style, query, graphql, rest, plugins:{}})
+
+//Ensure it's a well-formed SVG image
+  const parsed = libxmljs.parseXml(rendered)
+  if (parsed.errors.length)
+    throw new Error(`Malformed SVG : \n${parsed.errors.join("\n")}`)