Add test coverage check to CI

.travis.yml

@@ -9,6 +9,7 @@ install:
 
 script:
   - .travis/ci.sh
+  - .travis/coverage.sh
 
 after_success:
   - .travis/push.sh

.travis/coverage.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+
+min_coverage="${MIN_COVERAGE:-42}"
+line_coverage="$(CI=true yarn coverage | grep '^All files  *|' | cut -d'|' -f5 | tr -d ' ' | cut -d'.' -f1)"
+
+if [ ${line_coverage} -lt ${min_coverage} ]; then
+  echo "Got test coverage of ${line_coverage} which is less than configured minimum of ${min_coverage}" >&2
+  exit 1
+else
+  echo "Got test coverage of ${line_coverage}, well done" >&2
+  exit 0
+fi