feat(testing): Implement "assertSnapshot" #2039
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@@ -13,7 +13,7 @@ import { | |||||
| white, | ||||||
| } from "../fmt/colors.ts"; | ||||||
| import { fromFileUrl, parse, join } from "../path/mod.ts"; | ||||||
| import { ensureFile, ensureFileSync } from "../fs/mod.ts"; | ||||||
| import { diff, DiffResult, diffstr, DiffType } from "./_diff.ts"; | ||||||
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| const CAN_NOT_DISPLAY = "[Cannot display]"; | ||||||
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@@ -882,7 +882,7 @@ export async function assertSnapshot(context: Deno.TestContext, actual: unknown) | |||||
| snapshotFile = file ? JSON.parse(file) : {}; | ||||||
| } | ||||||
| const snapshot = snapshotFile?.[name]; | ||||||
| if (!Deno.args.includes('--update')) { | ||||||
| assertEquals(actual, snapshot); | ||||||
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There was a problem hiding this comment. The current implementation will error on: const actual = {
fn: () => { /* ... */ }
}As snapshots need to be represented as strings anyway, I would argue it makes more sense to use the {
"Snapshot Test > babo > merong": [
"{",
" b: 2,",
" c: 3,",
"}"
]
}This would enable us to catch a much wider range of errors in our snapshots. E.g. the following would error on // First run
const actual = {
testClass: class Test {}
}
// --snip--
assertSnapshot(test, actual)
// Second run
const actual = {
testClass: class NotTest {}
}
// --snip--
assertSnapshot(test, actual)But would not error (or worse, always error) if we only store the JSON representation. Additionally, this representation enables us to use the There was a problem hiding this comment. I think Deno.inspect() can be a good choice for serialization method. What do you think? @bcheidemann There was a problem hiding this comment. Yeah this would definitely do the job. I would suggest to use the |
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| } else { | ||||||
| let isEqual = true; | ||||||
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@@ -895,7 +895,7 @@ export async function assertSnapshot(context: Deno.TestContext, actual: unknown) | |||||
| } | ||||||
| updatedSnapshotFile[name] = actual; | ||||||
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There was a problem hiding this comment. Does this mean this implementation supports only 1 snapshot per test case? There was a problem hiding this comment. Does the test case mean one for example, if I test Deno.test("Snapshot Test A", async (t) => {
await assertSnapshot(t, { a: 1, b: 2 });
await t.step("yaho", async (t) => {
await assertSnapshot(t, { b: 2, c: 3 });
await t.step("haha", async (t) => {
await assertSnapshot(t, { b: 2, c: 4 });
});
});
});
Deno.test("Snapshot Test A2", async (t) => {
await assertSnapshot(t, { a: 1, b: 2 });
await t.step("what", async (t) => {
await assertSnapshot(t, { b: 2, c: 3 });
await t.step("good", async (t) => {
await assertSnapshot(t, { b: 2, c: 4 });
});
});
});the output, {
"Snapshot Test A": {
"a": 1,
"b": 2
},
"Snapshot Test A > yaho": {
"b": 2,
"c": 3
},
"Snapshot Test A > yaho > haha": {
"b": 2,
"c": 4
},
"Snapshot Test A2": {
"a": 1,
"b": 2
},
"Snapshot Test A2 > what": {
"b": 2,
"c": 3
},
"Snapshot Test A2 > what > good": {
"b": 2,
"c": 4
}
}There was a problem hiding this comment. How about the below case? I think the second Deno.test("Snapshot Test A", async (t) => {
await assertSnapshot(t, { a: 1, b: 2 });
await assertSnapshot(t, { c: 3, d: 4 });
});There was a problem hiding this comment. Aha! Sorry, now I know what you mean. That case will be handled with commented count. (Currently not implemented perfectly so I commented) @kt3k There was a problem hiding this comment. Ah, ok. I see. |
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| globalThis.onunload = writeSnapshotFileSync; | ||||||
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| // function getCount() { | ||||||
| // const count = snapshotMap?.[name] ? snapshotMap[name] : 1; | ||||||
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@@ -914,10 +914,11 @@ export async function assertSnapshot(context: Deno.TestContext, actual: unknown) | |||||
| return `${join(parts.dir, parts.name)}.snap`; | ||||||
| } | ||||||
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| function writeSnapshotFileSync() { | ||||||
| const snapshotPath = getSnapshotPath(); | ||||||
| ensureFileSync(snapshotPath); | ||||||
| const file = JSON.stringify(updatedSnapshotFile, null, 2); | ||||||
| Deno.writeTextFileSync(snapshotPath, file); | ||||||
| console.log('Snapshot updated!'); | ||||||
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There was a problem hiding this comment.
Suggested change
Maybe we could mimic Jest here and log how many snapshots were updated? |
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| } | ||||||
| } | ||||||
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@@ -9,6 +9,6 @@ | |
| }, | ||
| "Snapshot Test > babo > merong": { | ||
| "b": 2, | ||
| "c": 4 | ||
| } | ||
| } | ||
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Could do something like this to support
-uand--update.There was a problem hiding this comment.
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I will handle this after denoland/deno#14007 merged!
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BTW to pass
-uoption toDeno.args, you need to invoke test command likedeno test -- -ubecause the flags before--are consumed by Deno CLI itself. I'm ok with that for the first pass implementation, but it might be non ideal solution, I guessThere was a problem hiding this comment.
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Right. I also noticed that the flag for updating snapshot can affect other codes that wanted to test.. but I think that using
Deno.argsis better than making an option on Deno test cli.There was a problem hiding this comment.
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Imo this is the best solution for first pass. But if/when snapshot testing is a more established then we should look to implement this on the Deno CLI instead; as @hyp3rflow mentioned, this can affect test execution.