expect_length: Do you expect an object with this length or shape?

In testthat: Unit Testing for R

Do you expect an object with this length or shape?

Description

expect_length() inspects the length() of an object; expect_shape() inspects the "shape" (i.e. nrow(), ncol(), or dim()) of higher-dimensional objects like data.frames, matrices, and arrays.

Usage

expect_length(object, n)

expect_shape(object, ..., nrow, ncol, dim)

Arguments

object	Object to test. Supports limited unquoting to make it easier to generate readable failures within a function or for loop. See quasi_label for more details.
n	Expected length.
...	Not used; used to force naming of other arguments.
nrow, ncol	Expected nrow()/ncol() of object.
dim	Expected dim() of object.

See Also

expect_vector() to make assertions about the "size" of a vector.

Other expectations: comparison-expectations, equality-expectations, expect_error(), expect_match(), expect_named(), expect_null(), expect_output(), expect_reference(), expect_silent(), inheritance-expectations, logical-expectations

Examples

expect_length(1, 1)
expect_length(1:10, 10)
show_failure(expect_length(1:10, 1))

x <- matrix(1:9, nrow = 3)
expect_shape(x, nrow = 3)
show_failure(expect_shape(x, nrow = 4))
expect_shape(x, ncol = 3)
show_failure(expect_shape(x, ncol = 4))
expect_shape(x, dim = c(3, 3))
show_failure(expect_shape(x, dim = c(3, 4, 5)))

testthat documentation built on Nov. 25, 2025, 5:09 p.m.