Add istanbul checks for code coverage thresholds

packages/contracts/package.json

@@ -26,7 +26,7 @@
     "autogen:artifacts": "node scripts/generate-artifacts.js && node scripts/generate-deployed-artifacts.js",
     "test": "yarn test:contracts",
     "test:contracts": "hardhat test --show-stack-traces",
-    "test:coverage": "NODE_OPTIONS=--max_old_space_size=8192 hardhat coverage",
+    "test:coverage": "NODE_OPTIONS=--max_old_space_size=8192 hardhat coverage && istanbul check-coverage --statements 88 --branches 76 --functions 84 --lines 88",
     "test:slither": "slither .",
     "pretest:slither": "rm -f @openzeppelin && rm -f @ens && rm -f hardhat && ln -s ../../node_modules/@openzeppelin @openzeppelin && ln -s ../../node_modules/@ens @ens && ln -s ../../node_modules/hardhat hardhat",
     "posttest:slither": "rm -f @openzeppelin && rm -f @ens && rm -f hardhat",
@@ -88,6 +88,7 @@
     "hardhat": "^2.3.0",
     "hardhat-deploy": "^0.9.3",
     "hardhat-gas-reporter": "^1.0.4",
+    "istanbul": "^0.4.5",
     "lint-staged": "11.0.0",
     "lodash": "^4.17.21",
     "merkle-patricia-tree": "^4.0.0",

yarn.lock

@@ -9208,6 +9208,26 @@ istanbul-reports@^3.0.2:
     html-escaper "^2.0.0"
     istanbul-lib-report "^3.0.0"
 
+istanbul@^0.4.5:
+  version "0.4.5"
+  resolved "https://registry.yarnpkg.com/istanbul/-/istanbul-0.4.5.tgz#65c7d73d4c4da84d4f3ac310b918fb0b8033733b"
+  integrity sha1-ZcfXPUxNqE1POsMQuRj7C4Azczs=
+  dependencies:
+    abbrev "1.0.x"
+    async "1.x"
+    escodegen "1.8.x"
+    esprima "2.7.x"
+    glob "^5.0.15"
+    handlebars "^4.0.1"
+    js-yaml "3.x"
+    mkdirp "0.5.x"
+    nopt "3.x"
+    once "1.x"
+    resolve "1.1.x"
+    supports-color "^3.1.0"
+    which "^1.1.1"
+    wordwrap "^1.0.0"
+
 isurl@^1.0.0-alpha5:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/isurl/-/isurl-1.0.0.tgz#b27f4f49f3cdaa3ea44a0a5b7f3462e6edc39d67"