Reset the polluted database to ensure some tests work as expected

[Wang-Benjamin]

Problem

When the execution order of tests are shuffled, if tests (polluters) that make modifications on the database run before tests (victims) that rely on the original/unmodified database, the database will be polluted and victim tests will fail with assertionError.

Involved tests:

tk.mybatis.mapper.test.country.TestExistsWithPrimaryKey.testDynamicExistsWithPrimaryKey
tk.mybatis.mapper.test.country.TestInsert.testDynamicInsert
tk.mybatis.mapper.test.example.TestSelectByExample.testAndExample
tk.mybatis.mapper.test.example.TestSelectByExample.testAndOr
tk.mybatis.mapper.test.example.TestSelectByExample.testExcludeColumnsByExample
tk.mybatis.mapper.test.example.TestSelectByExample.testOrderBy
tk.mybatis.mapper.test.example.TestSelectByExample.testSelectByExample
tk.mybatis.mapper.test.example.TestSelectByExample.testSelectByExample2
tk.mybatis.mapper.test.example.TestSelectByExample.testSelectByExample3
tk.mybatis.mapper.test.example.TestSelectByExample.testSelectByExample4
tk.mybatis.mapper.test.example.TestSelectByExample.testSelectByExampleForUpdate
tk.mybatis.mapper.test.example.TestSelectByExample.testSelectByExampleInNotIn
tk.mybatis.mapper.test.example.TestSelectByExample.testSelectByExampleInNotIn2
tk.mybatis.mapper.test.example.TestSelectByExample.testSelectPropertisCheckCorrect

The above are all order-dependent victim tests and they test the properties of database without modification.

Take TestExistsWithPrimaryKey.testDynamicExistsWithPrimaryKey as an example:

Country country = new Country();
country.setId(35);
Assert.assertEquals(true, mapper.existsWithPrimaryKey(country));

country.setId(0);
Assert.assertEquals(false, mapper.existsWithPrimaryKey(country));

It expects country with id=35 exists in the database but it actually fails with assertionError if polluter tests that delete/modify the country with id=35 in the database run before it.

Proposed Fix

A simple and safe way to ensure victim tests can work as we expect is to reset/clean the database before executing such tests.

Glad to discuss this issue if you have concerns.