[start] .travis.yml

Does:
- Require a decent version of Node (v0.10.48 or something is... a tad old)
- Plan for sufficient resources for Chrome (garris/BackstopJS#603 (comment))
- Set up the show
- Wait for the show to be ready (i.e. busy-wait for port 3000 to serve)
- Run the test suite

Does not:
- Cut the test suite short when `yarn test --docker` returns nonzero exit code (as it most likely will, every single time)

Does not (yet):
- Auto-promote new Backstop state
- Regenerate dist
- Regenerate gh-pages

.travis.yml

@@ -0,0 +1,13 @@
+language: node_js
+node_js:
+  - lts/*
+
+services:
+  - docker   # For hermetic Backstop.js
+script: |
+  set -e -x
+  yarn start &
+  for retry in $(seq 1 30); do
+    if curl http://localhost:3000/ >/dev/null; then break; else sleep 5; fi
+  done
+  yarn test --docker || true

scripts/make_backstop_json.js

@@ -32,8 +32,10 @@ if (isForDocker) {
   if (os.platform() === "darwin") {
     serverHostname = "host.docker.internal";
   } else if (os.platform() === "linux") { // Also for Travis
-    // The important part being --net=host of course
-    testConfig.dockerCommandTemplate = "docker run --rm -it --net=host --mount type=bind,source=\"{cwd}\",target=/src backstopjs/backstopjs:{version} {backstopCommand} {args}";
+    // Changed from BackstopJS's DEFAULT_DOCKER_COMMAND_TEMPLATE:
+    // - --net=host
+    // - --shm-size=2gb and --cap-add=SYS_ADMIN as per https://github.com/garris/BackstopJS/issues/603#issuecomment-346478523
+    testConfig.dockerCommandTemplate = "docker run --rm -it --net=host --shm-size=2gb --cap-add=SYS_ADMIN --mount type=bind,source=\"{cwd}\",target=/src backstopjs/backstopjs:{version} {backstopCommand} {args}";
   } else {
     throw new Error(`Sorry, don't know how to run tests on ${os.platform()}`);
   }