Add tests for Redis HLL class

What does this MR do?

Add tests for Redis HLL class

Building testing case

week number	key	value	Notes
32	2020-32-{expand_vulnerabilities}	user_id_1	user 1 clicks one time in week 32
32	2020-32-{expand_vulnerabilities}	user_id_1	user 1 clicks second time in week 32
32	2020-32-{expand_vulnerabilities}	user_id_2	user 2 clicks one time in week 32
32	2020-32-{expand_vulnerabilities}	user_id_3	user 3 clicks one time in week 32
33	2020-33-{expand_vulnerabilities}	user_id_3	user 3 clicks one time in week 33
34	2020-34-{expand_vulnerabilities}	user_id_3	user 3 clicks one time in week 34
34	2020-34-{expand_vulnerabilities}	user_id_2	user 2 clicks one time in week 34

Results

• count of distinct users that performed expand_vulnerabilities actions for weeks 32, 33, 34 is 3
• count of distinct users that performed expand_vulnerabilities actions for weeks 32, 33 is 3
• count of distinct users that performed expand_vulnerabilities actions for weeks 33, 34 is 2

Code that I used for this example is

# Given data for 3 weeks and one  metric: metric base key `expand_vulnerabilities`
# Track one metric named `expand_vulnerabilities` 
# With 3 users

Gitlab::Redis::HLL.add(key: '2020-32-{expand_vulnerabilities}', value: "user_id_1", expiry: 29.days)
Gitlab::Redis::HLL.add(key: '2020-32-{expand_vulnerabilities}', value: "user_id_1", expiry: 29.days)
Gitlab::Redis::HLL.add(key: '2020-32-{expand_vulnerabilities}', value: "user_id_2", expiry: 29.days)
Gitlab::Redis::HLL.add(key: '2020-32-{expand_vulnerabilities}', value: "user_id_3", expiry: 29.days)

Gitlab::Redis::HLL.add(key: '2020-33-{expand_vulnerabilities}', value: "user_id_3", expiry: 29.days)

Gitlab::Redis::HLL.add(key: '2020-34-{expand_vulnerabilities}', value: "user_id_3", expiry: 29.days)
Gitlab::Redis::HLL.add(key: '2020-34-{expand_vulnerabilities}', value: "user_id_2", expiry: 29.days)

# count of distinct users that performed expand_vulnerabilities actions for weeks 32, 33, 34
Gitlab::Redis::HLL.count(keys: ["2020-32-{expand_vulnerabilities}", '2020-33-{expand_vulnerabilities}', '2020-34-{expand_vulnerabilities}'])
=> 3

count of distinct users that performed expand_vulnerabilities actions for weeks 32, 33
Gitlab::Redis::HLL.count(keys: ["2020-32-{expand_vulnerabilities}", '2020-33-{expand_vulnerabilities}'])
=> 3

# count of distinct users that performed expand_vulnerabilities actions for weeks 33, 34
Gitlab::Redis::HLL.count(keys: ['2020-33-{expand_vulnerabilities}', '2020-34-{expand_vulnerabilities}'])
=> 2

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Closes #235476 (closed)