Run tests in pool_test.go as subtests

[jholdstock]

This updates the "parent" test in pool_test.go to utilize the go testing framework's concept of subtests.

A new database is created for each subtest. This removes the need for each test to have its own specific clean up, and guarantees each test will have a clean database which is not contaminated by any previous tests. The performance penalty for repeatedly creating new databases is negligible.

Utilizing subtests allows the testing framework to provide more detailed feedback about the test run. Information about each subtest is logged, rather than just one log line for the parent test.

Managing the creation, cleaning and deleting of test databases in the "parent" test, outside of the "child" test files, is going to be useful for #257 because it is a good step towards allowing the test files to be database agnostic.

As an immediate example of how the detailed feedback can be useful, the example below shows that of the 10 second runtime, almost all of it is consumed by testClient. Previously this fact was hidden because it just appeared that the parent test TestPool was taking 10 seconds.

Log before (click to expand)

$ go test -v -count 1 ./...
?       github.com/decred/dcrpool       [no test files]
?       github.com/decred/dcrpool/cmd/miner     [no test files]
?       github.com/decred/dcrpool/gui   [no test files]
=== RUN   TestErrorKindStringer
--- PASS: TestErrorKindStringer (0.00s)
=== RUN   TestError
--- PASS: TestError (0.00s)
=== RUN   TestErrorKindIsAs
--- PASS: TestErrorKindIsAs (0.00s)
=== RUN   TestPool
--- PASS: TestPool (9.93s)
=== RUN   TestUpgrades
=== PAUSE TestUpgrades
=== CONT  TestUpgrades
=== RUN   TestUpgrades/group
=== RUN   TestUpgrades/group/test0
=== PAUSE TestUpgrades/group/test0
=== RUN   TestUpgrades/group/test1
=== PAUSE TestUpgrades/group/test1
=== RUN   TestUpgrades/group/test2
=== PAUSE TestUpgrades/group/test2
=== CONT  TestUpgrades/group/test0
=== CONT  TestUpgrades/group/test2
=== CONT  TestUpgrades/group/test1
--- PASS: TestUpgrades (0.00s)
    --- PASS: TestUpgrades/group (0.00s)
        --- PASS: TestUpgrades/group/test2 (0.00s)
        --- PASS: TestUpgrades/group/test0 (0.00s)
        --- PASS: TestUpgrades/group/test1 (0.00s)
PASS
ok      github.com/decred/dcrpool/pool  9.957s

Log after (click to expand)

$ go test -v -count 1 ./...
?       github.com/decred/dcrpool       [no test files]
?       github.com/decred/dcrpool/cmd/miner     [no test files]
?       github.com/decred/dcrpool/gui   [no test files]
=== RUN   TestDifficulty
--- PASS: TestDifficulty (0.00s)
=== RUN   TestErrorKindStringer
--- PASS: TestErrorKindStringer (0.00s)
=== RUN   TestError
--- PASS: TestError (0.00s)
=== RUN   TestErrorKindIsAs
--- PASS: TestErrorKindIsAs (0.00s)
=== RUN   TestLimiter
--- PASS: TestLimiter (0.00s)
=== RUN   TestPool
=== RUN   TestPool/testPaymentMgr
=== RUN   TestPool/testHub
=== RUN   TestPool/testInitDB
=== RUN   TestPool/testDatabase
=== RUN   TestPool/testShares
=== RUN   TestPool/testPayment
=== RUN   TestPool/testEndpoint
=== RUN   TestPool/testChainState
=== RUN   TestPool/testFetchBucketHelpers
=== RUN   TestPool/testAcceptedWork
=== RUN   TestPool/testAccount
=== RUN   TestPool/testJob
=== RUN   TestPool/testClient
--- PASS: TestPool (10.00s)
    --- PASS: TestPool/testPaymentMgr (0.12s)
    --- PASS: TestPool/testHub (0.02s)
    --- PASS: TestPool/testInitDB (0.01s)
    --- PASS: TestPool/testDatabase (0.01s)
    --- PASS: TestPool/testShares (0.00s)
    --- PASS: TestPool/testPayment (0.01s)
    --- PASS: TestPool/testEndpoint (0.10s)
    --- PASS: TestPool/testChainState (0.03s)
    --- PASS: TestPool/testFetchBucketHelpers (0.00s)
    --- PASS: TestPool/testAcceptedWork (0.01s)
    --- PASS: TestPool/testAccount (0.00s)
    --- PASS: TestPool/testJob (0.01s)
    --- PASS: TestPool/testClient (9.60s)
=== RUN   TestUpgrades
=== PAUSE TestUpgrades
=== CONT  TestUpgrades
=== RUN   TestUpgrades/group
=== RUN   TestUpgrades/group/test0
=== PAUSE TestUpgrades/group/test0
=== RUN   TestUpgrades/group/test1
=== PAUSE TestUpgrades/group/test1
=== RUN   TestUpgrades/group/test2
=== PAUSE TestUpgrades/group/test2
=== CONT  TestUpgrades/group/test0
=== CONT  TestUpgrades/group/test2
=== CONT  TestUpgrades/group/test1
--- PASS: TestUpgrades (0.00s)
    --- PASS: TestUpgrades/group (0.00s)
        --- PASS: TestUpgrades/group/test0 (0.00s)
        --- PASS: TestUpgrades/group/test1 (0.00s)
        --- PASS: TestUpgrades/group/test2 (0.00s)
PASS
ok      github.com/decred/dcrpool/pool  10.035s

Also:

• Remove Difficulty and Limiter tests from the parent test in pool_test.go. These can be run standalone with no issues.
• Move emptyBucket func from production code into test code (it is only used by tests)

[dnldd]

Nicely done.