Add test to confirm Math.random generates different first 3 decimal places

https://fastly.atlassian.net/browse/ECP-745

Author: Jake Champion

integration-tests/js-compute/fixtures/random/fastly.toml.in

@@ -0,0 +1,9 @@
+# This file describes a Fastly Compute@Edge package. To learn more visit:
+# https://developer.fastly.com/reference/fastly-toml/
+
+authors = ["[email protected]"]
+description = ""
+language = "javascript"
+manifest_version = 2
+name = "random"
+service_id = ""

integration-tests/js-compute/fixtures/random/random.js

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+function random3Decimals() {
+  return String(Math.random()).slice(0, 5);
+}
+
+let a = random3Decimals();
+let b = random3Decimals();
+
+addEventListener("fetch", event => {
+  if (a === b) {
+    return event.respondWith(new Response('The first 4 digits were repeated in sequential calls to Math.random() during wizening\n\n' + JSON.stringify({ a, b }, undefined, 4), { status: 500 }));
+  }
+
+  let c = random3Decimals();
+  let d = random3Decimals();
+  if (c === d) {
+    return event.respondWith(new Response('The first 4 digits were repeated in sequential calls to Math.random() during request handling\n\n' + JSON.stringify({ c, d }, undefined, 4), { status: 500 }));
+  }
+
+
+  return event.respondWith(new Response(JSON.stringify({ initialisedResults: [a, b], results: [c, d] }, undefined, 4)));
+});

integration-tests/js-compute/fixtures/random/tests.json

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+{
+  "GET /": {
+    "environments": ["viceroy", "c@e"],
+    "downstream_request": {
+      "method": "GET",
+      "pathname": "/"
+    },
+    "downstream_response": {
+      "status": 200,
+      "body": ""
+    }
+  }
+}