Can't run tests: unable to compile typescript

[mhansen]

mocha -r ts-node/register tests/test.ts

/usr/local/lib/node_modules/ts-node/src/index.ts:307
        throw new TSError(formatDiagnostics(diagnosticList, cwd, ts, lineOffset))
              ^
TSError: ⨯ Unable to compile TypeScript
tests/test.ts (1,25): Cannot find module 'assert' or its corresponding type declarations. (2307)
tests/test.ts (2,21): Cannot find module 'fs' or its corresponding type declarations. (2307)
    at getOutput (/usr/local/lib/node_modules/ts-node/src/index.ts:307:15)
    at /usr/local/lib/node_modules/ts-node/src/index.ts:336:16
    at Object.compile (/usr/local/lib/node_modules/ts-node/src/index.ts:498:11)
    at Module.m._compile (/usr/local/lib/node_modules/ts-node/src/index.ts:392:43)
    at Module._extensions..js (internal/modules/cjs/loader.js:1277:10)
    at Object.require.extensions.<computed> [as .ts] (/usr/local/lib/node_modules/ts-node/src/index.ts:395:12)
    at Module.load (internal/modules/cjs/loader.js:1105:32)
    at Function.Module._load (internal/modules/cjs/loader.js:967:14)
    at Module.require (internal/modules/cjs/loader.js:1145:19)
    at require (internal/modules/cjs/helpers.js:75:18)
    at /usr/local/lib/node_modules/mocha/lib/mocha.js:231:27
    at Array.forEach (<anonymous>)
    at Mocha.loadFiles (/usr/local/lib/node_modules/mocha/lib/mocha.js:228:14)
    at Mocha.run (/usr/local/lib/node_modules/mocha/lib/mocha.js:514:10)
    at Object.<anonymous> (/usr/local/lib/node_modules/mocha/bin/_mocha:480:18)
    at Module._compile (internal/modules/cjs/loader.js:1256:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1277:10)
    at Module.load (internal/modules/cjs/loader.js:1105:32)
    at Function.Module._load (internal/modules/cjs/loader.js:967:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:60:12)
    at internal/main/run_main_module.js:17:47