TypeError: Cannot set property X of #<Object> which has only a getter about esbuild HOT 2 OPEN

The behavior you are complaining about is an expected part of how ES modules work in JavaScript. For example:

$ node --input-type=module -e 'import * as fs from "fs"; Object.defineProperty(fs, "foo", { value: "bar" })'
file://./[eval1]:1
import * as fs from "fs"; Object.defineProperty(fs, "foo", { value: "bar" })
                                 ^

TypeError: Cannot redefine property: foo
    at Function.defineProperty (<anonymous>)
    at file://./[eval1]:1:34
    at ModuleJob.run (node:internal/modules/esm/module_job:218:25)
    at async ModuleLoader.eval (node:internal/modules/esm/loader:218:24)
    at async loadESM (node:internal/process/esm_loader:34:7)
    at async handleMainPromise (node:internal/modules/run_main:113:12)

Node.js v20.10.0

Since esbuild implements the JavaScript specification, esbuild does this too. Specifically the [[Set]] internal method of a module namespace exotic object in returns false, which then causes the PutValue abstract operation to throw a TypeError exception. So this is how the import statement is supposed to behave in JavaScript.

The testing libraries that you want to use are likely designed for CommonJS code and are not designed for use with ES modules (see sinonjs/sinon#2168 and thlorenz/proxyquire#217 for example).

from esbuild.

@evanw Looks like it might be an impossibility even with modern tools: https://www.npmjs.com/package/esmock
I'm using tsx for running typescript, which uses esbuild in the background.

from esbuild.