Move .test-cost.json

Also include parameter name in test output so that people will know what
to do to change the percent chance of failure.

Author: sandersn

scripts/costly-tests.js

@@ -25,7 +25,6 @@ async function main() {
         const percentTime = perf[k] / totalTime
         const percentHits = (1 + (edits[otherk] || 0)) / totalEdits
         const cost = 5 + Math.log(percentTime / percentHits)
-        // TODO: Write counts instead of numbers to make JSON file smaller
         data.push({ name: otherk, time: perf[k], edits: 1 + (edits[otherk] || 0), cost})
         if (edits[otherk])
             i++
@@ -36,7 +35,7 @@ async function main() {
         data: data.sort((x,y) => y.cost - x.cost).map(x => ({ ...x, cost: x.cost.toFixed(2) }))
     }
 
-    fs.writeFileSync('.test-cost.json', JSON.stringify(output), 'utf8')
+    fs.writeFileSync('tests/.test-cost.json', JSON.stringify(output), 'utf8')
 }
 
 main().catch(e => {

src/testRunner/parallel/host.ts

@@ -193,8 +193,8 @@ namespace Harness.Parallel.Host {
         }
 
         function skipCostlyTests(tasks: Task[]) {
-            if (statSync(".test-cost.json")) {
-                const costs = JSON.parse(readFileSync(".test-cost.json", "utf8")) as {
+            if (statSync("tests/.test-cost.json")) {
+                const costs = JSON.parse(readFileSync("tests/.test-cost.json", "utf8")) as {
                     totalTime: number,
                     totalEdits: number,
                     data: { name: string, time: number, edits: number, costs: number }[]
@@ -208,7 +208,7 @@ namespace Harness.Parallel.Host {
                     skippedTime += costs.data[i].time;
                     skippedTests.add(costs.data[i].name);
                 }
-                console.log(`Skipped ${i} expensive tests; estimated time savings of ${(skippedTime / costs.totalTime * 100).toFixed(2)}% with ${skipPercent.toFixed(2)}% chance of missing a test.`);
+                console.log(`Skipped ${i} expensive tests; estimated time savings of ${(skippedTime / costs.totalTime * 100).toFixed(2)}% with --skipPercent=${skipPercent.toFixed(2)} chance of missing a test.`);
                 return tasks.filter(t => !skippedTests.has(t.file));
             }
             else {