Junit5: Argument Conversion

Junit5 supports automatic arguments conversion. There are three types of conversions.

a.   Widening Conversion

b.   Implicit Conversion

c.    Explicit Conversion

 

Widening Conversion

Junit supports widening of primitive types that are supplied to @ParameterizedTest.

 

Example

byte to short, int, long, float, or double

short to int, long, float, or double

char to int, long, float, or double

int to long, float, or double

long to float or double

float to double

 

For example, a parameterized test annotated with @ValueSource(ints = { 1, 2, 3 }) can be declared to accept not only an argument of type int but also an argument of type long, float, or double.

 

Reference

https://docs.oracle.com/javase/specs/jls/se8/html/jls-5.html#jls-5.1.2

 

Implicit Conversion

Junit has number of built-in implicit type converters.

 

Below table summarizes how the implicit type conversion happen.

 

Target Type	Example
boolean/Boolean	"true" → true
byte/Byte	"15", "0xF", or "017" → (byte) 15
char/Character	"o" → 'o'
short/Short	"15", "0xF", or "017" → (short) 15
int/Integer	"15", "0xF", or "017" → 15
long/Long	"15", "0xF", or "017" → 15L
float/Float	"1.0" → 1.0f
double/Double	"1.0" → 1.0d
Enum subclass	"SECONDS" → TimeUnit.SECONDS
java.io.File	"/path/to/file" → new File("/path/to/file")
java.lang.Class	"java.lang.Integer" → java.lang.Integer.class (use $ for nested classes, e.g. "java.lang.Thread$State")
java.lang.Class	"byte" → byte.class (primitive types are supported)
java.lang.Class	"char[]" → char[].class (array types are supported)
java.math.BigDecimal	"123.456e789" → new BigDecimal("123.456e789")
java.math.BigInteger	"1234567890123456789" → new BigInteger("1234567890123456789")
java.net.URI	"https://junit.org/" → URI.create("https://junit.org/")
java.net.URL	"https://junit.org/" → new URL("https://junit.org/")
java.nio.charset.Charset	"UTF-8" → Charset.forName("UTF-8")
java.nio.file.Path	"/path/to/file" → Paths.get("/path/to/file")
java.time.Duration	"PT3S" → Duration.ofSeconds(3)
java.time.Instant	"1970-01-01T00:00:00Z" → Instant.ofEpochMilli(0)
java.time.LocalDateTime	"2017-03-14T12:34:56.789" → LocalDateTime.of(2017, 3, 14, 12, 34, 56, 789_000_000)
java.time.LocalDate	"2017-03-14" → LocalDate.of(2017, 3, 14)
java.time.LocalTime	"12:34:56.789" → LocalTime.of(12, 34, 56, 789_000_000)
java.time.MonthDay	"--03-14" → MonthDay.of(3, 14)
java.time.OffsetDateTime	"2017-03-14T12:34:56.789Z" → OffsetDateTime.of(2017, 3, 14, 12, 34, 56, 789_000_000, ZoneOffset.UTC)
java.time.OffsetTime	"12:34:56.789Z" → OffsetTime.of(12, 34, 56, 789_000_000, ZoneOffset.UTC)
java.time.Period	"P2M6D" → Period.of(0, 2, 6)
java.time.YearMonth	"2017-03" → YearMonth.of(2017, 3)
java.time.Year	"2017" → Year.of(2017)
java.time.ZonedDateTime	"2017-03-14T12:34:56.789Z" → ZonedDateTime.of(2017, 3, 14, 12, 34, 56, 789_000_000, ZoneOffset.UTC)
java.time.ZoneId	"Europe/Berlin" → ZoneId.of("Europe/Berlin")
java.time.ZoneOffset	"+02:30" → ZoneOffset.ofHoursMinutes(2, 30)
java.util.Currency	"JPY" → Currency.getInstance("JPY")
java.util.Locale	"en" → new Locale("en")
java.util.UUID	"d043e930-7b3b-48e3-bdbe-5a3ccfb833db" → UUID.fromString("d043e930-7b3b-48e3-bdbe-5a3ccfb833db")

 

 

 

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