assert: Assertions with a message
In InsightRX/json2test: Run R package tests specified in JSON

Description Usage Arguments Value Note Examples

The function assert() was built from stopifnot(). It emits a message in case of errors, which can be a helpful hint for diagnosing the errors (stopifnot() only prints the possibly truncated source code of the expressions).

The infix operator %==% is simply an alias of the identical() function to make it slightly easier and intuitive to write test conditions. x %==% y is the same as identical(x, y).

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assert(func, fact, time = NA, ...)

x %==% y

`func`	name of the function to test
`fact`	a message for the assertions when any of them fails; treated the same way as expressions in `...` if it is not a character string, which means you do not have to provide a message to this function
`time`	time the test takes to run
`...`	any number of R expressions, presumably to return vectors of `TRUE`'s (if `FALSE` is returned anywhere, an error will show up)
`x, y`	two R objects to be compared

Invisible NULL if all expressions returned TRUE, otherwise an error is signalled and the user-provided message is emitted.

The internal implementation of stopifnot() is different with the function in R base: (1) the custom message fact is emitted if an error occurs (2) assert() requires the logical values to be non-empty (3) if ... contains a compound expression in {} which returns FALSE (e.g., if (TRUE) {1+1; FALSE}), the first and the last but one line of the source code from deparse() are printed in the error message, otherwise the first line is printed

assert('one equals one', 1==1)
assert('seq and : produce equal sequences', seq(1L, 10L) == 1L:10L)
assert('seq and : produce identical sequences', identical(seq(1L, 10L), 1L:10L))

# multile tests
T=FALSE; F=TRUE
assert('T is bad for TRUE, and so is F for FALSE', T!=TRUE, F!=FALSE)

# a mixture of tests
assert("Let's pray all of them will pass", 1==1, 1!=2, letters[4]=='d', rev(rev(letters))==letters)

# logical(0) cannot pass assert(), although stopifnot() does not care
try(assert('logical(0) cannot pass', 1==integer(0)))
stopifnot(1==integer(0)) # it's OK!

# a compound expression
try(assert('this if statement returns TRUE', if(TRUE){x=1;x==2}))

# no message
assert(!FALSE, TRUE, is.na(NA))