[EC-423] Fix unit tests (#3265)

* Create base jest.config file

* Fix various tests that were broken

* Add maxWorkers to jest config

* Undo change to testEnvironment

* Enable tsconfig.spec.json

libs/shared/jest.config.base.js

@@ -0,0 +1,19 @@
+/* eslint-env node */
+module.exports = {
+  testMatch: ["**/+(*.)+(spec).+(ts)"],
+  collectCoverage: true,
+  coverageReporters: ["html", "lcov"],
+  coverageDirectory: "coverage",
+
+  // Workaround for a memory leak that crashes tests in CI:
+  // https://github.com/facebook/jest/issues/9430#issuecomment-1149882002
+  // Also anecdotally improves performance when run locally
+  maxWorkers: 3,
+
+  // Jest does not use tsconfig.spec.json by default
+  globals: {
+    "ts-jest": {
+      tsconfig: "<rootDir>/tsconfig.spec.json",
+    },
+  },
+};