Solidity Testing – How to Unit Test Contract Private and Internal Functions

I have written more than a thousand tests for different smart contracts and can say that you will almost always want to use javascript/mocha with truffle. There are very few cases that I have run into where you will want to use solidity instead. It is just so much easier to setup your contracts to the state that you want in order to run the tests.

Also... you really don't need to chain up function calls like in the example given. You can use async/await which will make things MUCH cleaner and readable. I have created a boilerplate truffle project which I use for any of my new projects. I keep it updated with examples etc. I would highly recommend checking out the way tests are in there...

repo:

https://github.com/TovarishFin/smart-contract-boilerplate

direct link to a test file using async/await:

https://github.com/TovarishFin/smart-contract-boilerplate/blob/master/test/ExampleCoin.js

I've written test.js to show the example of how you can test this modifier:

var MyContract = artifacts.require("MyContract")

contract('MyContract', (accounts) => {

  let instance
  let owner = accounts[0]
  let account = accounts[1]

  beforeEach(async () => {
    instance = await MyContract.deployed()
  })

  it("should check restriction", async () => {
    try {
      let result = await instance.restrictedFunction.call({from: account})
      assert.equal(result.toString(), owner)
    } catch (e) {
      console.log(`${account} is not owner`)
    }
  })
})

In this example the test will not fail in both cases; I made it this way because it depends what result you are willing to get from this particular test. If you want it to fail if account is not owner, make this edit:

} catch (e) {
      assert.fail(null, null, `${account} is not owner`)
}