50 lines
1.5 KiB
Markdown
50 lines
1.5 KiB
Markdown
The test demonstrates one of the temptations a developer meets when writing tests.
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What we have here is actually 3 tests, but layed out as a single function with 3 asserts.
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Sometimes it's easier to write this way, but if an error occurs, it's much less obvious what went wrong.
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If an error happens inside a complex execution flow, then we'll have to figure out the data at that point. We'll actually have to *debug the test*.
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It would be much better to break the test into multiple `it` blocks with clearly written inputs and outputs.
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Like this:
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```js
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describe("Raises x to power n", function() {
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it("5 in the power of 1 equals 5", function() {
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assert.equal(pow(5, 1), 5);
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});
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it("5 in the power of 2 equals 25", function() {
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assert.equal(pow(5, 2), 25);
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});
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it("5 in the power of 3 equals 125", function() {
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assert.equal(pow(5, 3), 125);
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});
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});
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```
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We replaced the single `it` with `describe` and a group of `it` blocks. Now if something fails we would see clearly what the data was.
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Also we can isolate a single test and run it in standalone mode by writing `it.only` instead of `it`:
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```js
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describe("Raises x to power n", function() {
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it("5 in the power of 1 equals 5", function() {
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assert.equal(pow(5, 1), 5);
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});
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*!*
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// Mocha will run only this block
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it.only("5 in the power of 2 equals 25", function() {
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assert.equal(pow(5, 2), 25);
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});
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*/!*
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it("5 in the power of 3 equals 125", function() {
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assert.equal(pow(5, 3), 125);
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});
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});
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```
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