AssertJ SchemaCrawler - Fluent Assertions for SchemaCrawler

Motivation

Writing junit tests with SchemaCrawler is powerful to check the consistency of a data model change executed using some database migrator like flyway or liquibase. The catalog api is well designed but also very complex. So it's hard to getting in and the resulting assertion code has a lot of boilerplate and looks like a mess:

Table table = catalog.lookupTable(
  catalog.lookupSchema("EXAMPLE_SCHEMA").orElseThrow(),
  "EXAMPLE_ENTITY1").orElseThrow();

assertThat(table.lookupColumn("ENTITY1_ID")).get()
  .satisfies(x -> {
    assertThat(x.getColumnDataType().getName()).isEqualTo("CHAR");
    assertThat(x.getSize()).isEqualTo(36);
  });

assertThat(table.lookupColumn("ATTRIBUTE1")).get()
  .satisfies(x -> {
    assertThat(x.getColumnDataType().getName()).isEqualTo("VARCHAR");
    assertThat(x.getSize()).isEqualTo(250);
  });

assertThat(table.lookupTableConstraint("EXAMPLE_ENTITY1_PK"))
  .get()
  .extracting(TableConstraint::getConstrainedColumns)
  .asInstanceOf(InstanceOfAssertFactories.list(TableConstraint.class))
  .anyMatch(x -> x.getName().equals("ENTITY1_ID"));

Using assertj-schemacrawler the code reduces to:

TableAssert table = SchemaCrawlerAssertions.assertThat(catalog)
  .table("EXAMPLE_SCHEMA", "EXAMPLE_ENTITY1");

table.column("ENTITY1_ID")
  .matchesColumnDataTypeName(Predicate.isEqual("CHAR"))
  .matchesSize(Predicate.isEqual(36));

table.column("ATTRIBUTE1")
  .matchesColumnDataTypeName(Predicate.isEqual("VARCHAR"))
  .matchesSize(Predicate.isEqual(250));

table.tableConstraint("EXAMPLE_ENTITY1_PK")
  .constrainedColumns()
  .anyMatch(x -> x.getName().equals("ENTITY1_ID"));

Getting Started

Crawl the database catalog using the java library (see how to ).

Include

<dependency>
  <groupId>io.github.bekoenig</groupId>
  <artifactId>assertj-schemacrawler</artifactId>
  <version>*current version*</version>
  <scope>test</scope>
</dependency>

in your project.

The class SchemaCrawlerAssertions is the entry point and contains assertThat overloads for all schema crawler types.

Catalog catalog = ...;

SchemaCrawlerAssertions
  .assertThat(catalog)
  .table("EXAMPLE_SCHEMA", "EXAMPLE_ENTITY1").isNotNull()

The class SchemaCrawlerInstanceOfAssertFactories contains factory methods to provide implementations for InstanceOfAssertFactory. This is useful to produce a new assert narrowed to that type using asInstanceOf.

columnAssert.parent()
  .asInstanceOf(SchemaCrawlerInstanceOfAssertFactories.table())
  .column("ATTRIBUTE1");

Conventions

Each assert class is derivated from comparable or object assert and contains an assert method for each api method of the associated schema crawler type.

The assert methods follow this naming pattern:

method of SchemaCrawler type	assertion method
primitive type getSomething()	matchesSomething(Predicate< primitive type >)
complex type getSomething()	satisfiesSomething(Consumer< complex type >)
boolean is- or hasSomething()	is- or hasSomething(boolean)
list or collection getSomethings()	specific assert for list or collection with element support somethings()
optional lookupSomething(String)	specific assert for something with nullable on empty something(String)
complex type getParent()	object assert for complex type parent()

Compatibility

Even if this library is a standalone project (see SchemaCrawler Issue 1544) the goal is to provide a maximum compatibility to the latest version of schema crawler using state of the art coding style of assertj.