Room unexpected behavior when working with BLOB & TEXT - sqlite

Question

I am migrating my app's SQLite helper to Room. Basically what I am doing is just copying data from old SQLite database to Room, so due to schema mismatch I need to provide migration. I am having this issue with BLOB data in Room.
I have below simple model
class NewCourse {
var weekday: Array<String> = arrayOf()
}
I also have TypeConverter as
#TypeConverter
fun toArray(concatenatedStrings: String?): Array<String>? {
return concatenatedStrings?.split(",".toRegex())?.dropLastWhile { it.isEmpty() }?.toTypedArray()
}
#TypeConverter
fun fromArray(strings: Array<String>?): String? {
return strings?.joinToString(",")
}
Within my old appdatabase.db database I have a corresponding table Course with a field weekday which has a type BLOB.
Well, because of my TypeConverter in room database I will have weekday with a type TEXT. While migrating I running below SQL script.
INSERT INTO NewCourse (weekday) SELECT weekday FROM Course
As weekday from Course table is BLOB type and in SQL you can basically store anything to anything, am I expecting it will copy BLOB-typed weekday in Course to TEXT-typed weekday in NewCourse.
Well at first I was expecting some error due to type mismatch. But "fortunately", but not expectedly, Room doesn't throw any exception and it gets value of BLOB and copies as TEXT.
My first question was why it is working? i.e. how it's copying the TEXT value of BLOB to my newly created table?
I never cared about it, as it was working perfectly, until I did some testing with Robolectic.
Unfortunately, I am getting error if I start testing with Robolectic. After copying data in my migration, when I query for NewCourse I am getting SQL error of
android.database.sqlite.SQLiteException: Getting string when column is blob. Row 0, col 10
So, I suppose here it is copying the data as BLOB and when querying for weekday it is throwing an exception as getWeekDay calls getString of cursor.
My second question would be "Why while testing with Robolectic it is not working as it is working with just running the app?"
I also tested the queries with just Sql not involving Android, and over there it copies the BLOB as BLOB even though the type of weekday at NewCourse is TEXT as expected.

Answer 1

Robolectric is a testing library for android applications. The keyword here is testing and by that it means there shouldn't be any exception. Robolectric showing you error maybe because of some android devices may throw exception so your application will crash. Try checking your logs while your application running. Maybe you are missing some warnings.