/approval-tests

Java Scrubbers

Scrubbers normalize dynamic data before comparison. Flaky tests across environments usually means unscrubbed timestamps, UUIDs, ports, or paths.

Contents

• Imports
• Built-in Scrubbers
• RegExScrubber
• Combining Scrubbers
• Using with Options
• Custom Scrubber
• Common Patterns
• Built-in Utility Scrubbers

For Options usage patterns, see api.md.

Imports

import org.approvaltests.scrubbers.*;
import org.approvaltests.core.Options;

Built-in Scrubbers

GuidScrubber

Replaces UUIDs with guid_1, guid_2, etc.

String[] guids = {
    "2fd78d4a-ad49-447d-96a8-deda585a9aa5",
    "2fd78d4a-1111-1111-1111-deda585a9aa5"
};
Approvals.verifyAll("guids", guids, new Options(Scrubbers::scrubGuid));

Output:

guids[0] = guid_1
guids[1] = guid_2

DateScrubber

Auto-detects date format from example:

Scrubber scrubber = DateScrubber.getScrubberFor("00:00:00");
Approvals.verify("created at 03:14:15", new Options().withScrubber(scrubber));

Output: created at [Date1]

Supported Date Formats

Pass an example date to getScrubberFor():

• 23:30:00 - Time only
• 2024-12-17 - ISO date
• 2020-09-10T08:07Z - ISO 8601 short
• 2020-09-10T08:07:89Z - ISO 8601 with seconds
• 2020-09-10T01:23:45.678Z - ISO 8601 with milliseconds
• 2024-12-18T14:04:46.746130Z - ISO 8601 with nanoseconds
• 20210505T091112Z - Compact ISO format
• 2014/05/13 16:30:59.786 - Slash-separated with ms
• 2025-05-15 16:57:04.599 - Datetime with space
• Tue May 13 16:30:00 - Day Mon DD HH:MM:SS
• Wed Nov 17 22:28:33 EET 2021 - With timezone name
• Tue May 13 16:30:00 -0800 2014 - With timezone offset
• 13 May 2014 23:50:49,999 - DD Mon YYYY HH:MM:SS,ms
• May 13, 2014 11:30:00 PM PST - Mon DD, YYYY HH:MM:SS AM/PM TZ
• 13/05/2014 23:50:49 - DD/MM/YYYY with separators (., -, /)
• Wed, 21 Oct 2015 07:28:00 GMT - RFC 2822

Custom Date Format

DateScrubber.addScrubber("2023-Dec-25", "\\d{4}-[A-Za-z]{3}-\\d{2}");
Scrubber scrubber = DateScrubber.getScrubberFor("2023-Dec-25");

With SimpleDateFormat

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
DateScrubber scrubber = DateScrubber.forSimpleDateFormat(sdf);

RegExScrubber

Static Replacement

Scrubber scrubber = new RegExScrubber("\\d+", "[number]");
Approvals.verify("Count: 42", new Options(scrubber));
// Output: Count: [number]

Dynamic Replacement

Scrubber scrubber = new RegExScrubber("user_\\d+", n -> "user_" + n);
Approvals.verify("user_123 and user_456", new Options(scrubber));
// Output: user_1 and user_2

Combining Scrubbers

Scrubbers.scrubAll()

Scrubber portScrubber = new RegExScrubber(":\\d+/", ":[port]/");
Scrubber dateScrubber = DateScrubber.getScrubberFor("20210505T091112Z");
Scrubber signatureScrubber = new RegExScrubber("Signature=.+", "Signature=[sig]");

Scrubber combined = Scrubbers.scrubAll(portScrubber, dateScrubber, signatureScrubber);

Approvals.verify(
    "http://127.0.0.1:55079/foo?Date=20210505T091112Z&Signature=4a7dd6f",
    new Options(combined)
);

Output: http://127.0.0.1:[port]/foo?Date=[Date1]&Signature=[sig]

MultiScrubber Class

Scrubber combined = new MultiScrubber(
    Arrays.asList(scrubber1, scrubber2, scrubber3)
);

Using with Options

Constructor

Approvals.verify(data, new Options(Scrubbers::scrubGuid));

withScrubber Method

Options options = new Options()
    .withScrubber(DateScrubber.getScrubberFor("2024-01-15"));
Approvals.verify(data, options);

Custom Scrubber

Implement the Scrubber interface:

Scrubber myScrubber = input -> input
    .replaceAll("Bearer [a-zA-Z0-9]+", "Bearer [TOKEN]")
    .replaceAll("\\d{10}", "[TIMESTAMP]");

Approvals.verify(apiResponse, new Options(myScrubber));

Common Patterns

Scrub API Response

Scrubber apiScrubber = Scrubbers.scrubAll(
    new GuidScrubber(),
    DateScrubber.getScrubberFor("2024-01-15T10:30:00Z"),
    new RegExScrubber("\"id\":\\s*\\d+", "\"id\": [ID]")
);

JsonApprovals.verifyAsJson(response, new Options(apiScrubber));

Scrub Timestamps

Scrubber scrubber = Scrubbers.scrubAll(
    DateScrubber.getScrubberForTimestamp(),
    DateScrubber.getScrubberForSqlDate()
);

Built-in Utility Scrubbers

• Scrubbers.scrubGuid(input) - Scrub UUIDs
• DateScrubber.getScrubberForTimestamp() - Java Timestamp
• DateScrubber.getScrubberForSqlDate() - SQL Date
• DateScrubber.getScrubberForDate() - Java Date