utdatagen

A very small java library to create test data for Unit Tests.

Usage instructions -

1. Create an instance of a DBTableFixture pointing to a single DB table
2. Use the truncateTable() method on the instance to delete existing data (optional)
3. Use the InsertionCriteria class to specify powerful/flexible plans to insert some data with various patterns
4. Test your data-access/manipulation code on the generated data
5. If needed, use the methods on the DBTableFixture instance to retrieve data in the table and assert against it

Please refer to these tests for basic sample usage -
https://github.com/webashutosh/utdatagen/blob/master/src/test/java/in/acode/utdatagen/DBTableFixtureMySqlTest.java

Demo for using built-in value suppliers AND for building your own column value suppliers- https://github.com/webashutosh/utdatagen/blob/master/src/test/java/in/acode/utdatagen/CustomValueSuppliersTest.java

Crux of how it all works -

• When creating an InsertionCriteria, you have to specify two main things -
  • the number of rows to be inserted (n)
  • optionally, a value-supplier for some/all columns
• When you start inserting rows, the DBTableFixture generates n rows in a loop, one at a time
• For generating a single row, it has to get values for all the columns. It does so as following -
  • If the user specified a value-supplier, it calls that to get the value
    • Value-suppliers have access to the index of the row being inserted AND the value inserted for the previous row - this info can be used while generating the value for the current row
  • Else, it checks if the column is nullable
  • If it is, it leaves it as null
  • Else, it generates a random default value (it tries best to make sure that the value fits in the DB column restrictions). For details - please refer to DBColumnMetadata.java
  • Note - users can indicate that they want nullable columns to have values, in which case, a random default value is used
• Once all rows are generated in memory, they are inserted to the DB