Hi! Is there any way to simulate a select failure ...

# exposed

[cincue]

Hi! Is there any way to simulate a select failure with DSL API during testing?

[Evan R.]

You could use MockK to mock your table to throw ExposedSQLException

[Evan R.]

https://mockk.io/#object-mocks

[cincue]

Hi Evan! Could you provide an example? Thanks!

[Evan R.]

Assuming you already have a database table such as this (doing this without an IDE, calls may be slightly incorrect):

object MyTable : IntIdTable {
  val name = varchar("name", 128)
}

You can use MockK to mock the “select” method, like:

mockkObject(MyTable)
every { MyTable.select(any()) } throws ExposedSQLException( /* Add params for exception here */ )

assertThrows(ExposedSQLException) { MyTable.select { MyTable.id eq 1 } }

// Use this to undo mock
unmockkObject(MyTable)

[cincue]

I'm trying Mockk and I have the same problem as with Mockito, I get "java.lang.IllegalStateException: No transaction in context.", I suspected that It could happen. Any ideas?

[Evan R.]

Sounds like you may be mocking the wrong method. That exception shouldn’t be thrown if the actual method is mocked

[cincue]

I tried with your snippet and It didn't work.

[Evan R.]

Found the issue. Turns out .select() is an extension function. The following snippet worked for me:

mockkStatic("org.jetbrains.exposed.sql.QueriesKt")
every { MyTable.select(any<Op<Boolean>>()) } throws mockk<ExposedSQLException>()

assertThrows<ExposedSQLException> { MyTable.select { MyTable.id eq 5 } }

[Evan R.]

Extension functions aren’t actually part of the object itself, they are compiled to static methods on a synthetic class created for the file.

To mock it you need to perform a static mock of the file containing the extension function, in this case QueriesKt (from org.jetbrains.exposed.sql.Queries.kt)

[cincue]

Great!! Thanks Evan! It works

[Evan R.]

Glad to hear it!