13. Unit Testing
The YOLO-mode query checking feature demonstated in an earlier chapter is also available as a trait you can mix into your Specs2 or ScalaTest unit tests.
Setting Up
As with earlier chapters we set up a Transactor and YOLO mode. We will also use the doobie-specs2-cats and doobie-scalatest-cats add-ons.
import doobie.imports._
import cats._, cats.data._, cats.implicits._
import fs2.interop.cats._
val xa = DriverManagerTransactor[IOLite](
"org.postgresql.Driver", "jdbc:postgresql:world", "postgres", ""
)
And again we are playing with the country table, given here for reference.
CREATE TABLE country (
code character(3) NOT NULL,
name text NOT NULL,
population integer NOT NULL,
gnp numeric(10,2),
indepyear smallint
-- more columns, but we won't use them here
)
So here are a few queries we would like to check. Note that we can only check values of type Query0 and Update0; we can’t check Process or ConnectionIO values, so a good practice is to define your queries in a DAO module and apply further operations at a higher level.
case class Country(code: Int, name: String, pop: Int, gnp: Double)
val trivial = sql"""
select 42, 'foo'::varchar
""".query[(Int, String)]
def biggerThan(minPop: Short) = sql"""
select code, name, population, gnp, indepyear
from country
where population > $minPop
""".query[Country]
def update(oldName: String, newName: String) = sql"""
update country set name = $newName where name = $oldName
""".update
The Specs2 Package
The doobie-specs2-cats add-on provides a mix-in trait that we can add to a Specification to allow for typechecking of queries, interpreted as a set of specifications.
Our unit test needs to extend AnalysisSpec and must define a Transactor[IOLite]. To construct a testcase for a query, pass it to the check method. Note that query arguments are never used, so they can be any values that typecheck.
import doobie.util.iolite.IOLite
import doobie.specs2.imports._
import org.specs2.mutable.Specification
object AnalysisTestSpec extends Specification with AnalysisSpec {
val transactor = DriverManagerTransactor[IOLite](
"org.postgresql.Driver", "jdbc:postgresql:world", "postgres", ""
)
check(trivial)
check(biggerThan(0))
check(update("", ""))
}
When we run the test we get output similar to what we saw in the previous chapter on checking queries, but each item is now a test. Note that doing this in the REPL is a little awkward; in real source you would get the source file and line number associated with each query.
scala> { specs2 run AnalysisTestSpec; () } // pretend this is sbt> test
[info] $line12.$read$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$AnalysisTestSpec$
[info]
[info] +
Query0[(Int, String)] defined at <console>:28
select 42, 'foo'::varchar
[info] + C01 ?column? INTEGER (int4) NULL? → Int
[info] + C02 varchar VARCHAR (varchar) NULL? → String
[info] +
Query0[Country] defined at <console>:30
select code, name, population, gnp, indepyear
from country
where population > ?
[info] + SQL Compiles and Typechecks
[error] x P01 Short → INTEGER (int4)
[error] x Short is not coercible to INTEGER (int4) according to the JDBC specification.
Fix this by changing the schema type to SMALLINT, or the Scala type to Int or
JdbcType. (file:1)
[error] x C01 code CHAR (bpchar) NOT NULL → Int
[error] x CHAR (bpchar) is ostensibly coercible to Int according to the JDBC specification
but is not a recommended target type. Fix this by changing the schema type to
INTEGER; or the Scala type to Code or PersonId or String. (file:1)
[info] + C02 name VARCHAR (varchar) NOT NULL → String
[info] + C03 population INTEGER (int4) NOT NULL → Int
[info]
[error] x C05 indepyear SMALLINT (int2) NULL →
[error] x Column is unused. Remove it from the SELECT statement. (file:1)
[info]
[info] +
Update0 defined at <console>:28
update country set name = ? where name = ?
[info] + SQL Compiles and Typechecks
[info] + P01 String → VARCHAR (varchar)
[info] + P02 String → VARCHAR (text)
[info]
[info]
[info] Total for specification $line12.$read$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$AnalysisTestSpec$
[info] Finished in 748 ms
16 examples, 4 failures, 0 error
[info]
The ScalaTest Package
The doobie-scalatest-cats add-on provides a mix-in trait that we can add to any Assertions implementation (like FunSuite) much like the Specs2 package above.
import doobie.scalatest.imports._
import org.scalatest._
class AnalysisTestScalaCheck extends FunSuite with Matchers with IOLiteChecker {
val transactor = DriverManagerTransactor[IOLite](
"org.postgresql.Driver", "jdbc:postgresql:world", "postgres", ""
)
test("trivial") { check(trivial) }
test("biggerThan") { check(biggerThan(0)) }
test("update") { check(update("", "")) }
}
Details are shown for failing tests.
scala> (new AnalysisTestScalaCheck).execute() // pretend this is sbt> test
AnalysisTestScalaCheck:
- trivial
- biggerThan *** FAILED ***
Query0[Country] defined at <console>:30
select code, name, population, gnp, indepyear
from country
where population > ?
✓ SQL compiles and typechecks
✕ P01 Short → INTEGER (int4)
- Short is not coercible to INTEGER (int4) according to the JDBC specification.
Fix this by changing the schema type to SMALLINT, or the Scala type to Int or
JdbcType.
✕ C01 code CHAR (bpchar) NOT NULL → Int
- CHAR (bpchar) is ostensibly coercible to Int according to the JDBC specification
but is not a recommended target type. Fix this by changing the schema type to
INTEGER; or the Scala type to Code or PersonId or String.
✓ C02 name VARCHAR (varchar) NOT NULL → String
✓ C03 population INTEGER (int4) NOT NULL → Int
✕ C04 gnp NUMERIC (numeric) NULL → Double
- NUMERIC (numeric) is ostensibly coercible to Double according to the JDBC
specification but is not a recommended target type. Fix this by changing the
schema type to FLOAT or DOUBLE; or the Scala type to BigDecimal or BigDecimal.
- Reading a NULL value into Double will result in a runtime failure. Fix this by
making the schema type NOT NULL or by changing the Scala type to Option[Double]
✕ C05 indepyear SMALLINT (int2) NULL →
- Column is unused. Remove it from the SELECT statement. (Checker.scala:102)
- update