rxTest({
  test_that("'drop' test", {

    ode <- rxode2("
         d/dt(X) = a*X + Y*Z;
         d/dt(Y) = b*(Y - Z);
         d/dt(Z) = -X*Y + c*Y - Z;")

    et <- eventTable() # default time units
    et$add.sampling(seq(from = 0, to = 10, by = 1))

    out0 <- rxSolve(ode,
                    params = c(a = -8 / 3, b = -10, c = 28),
                    events = et, inits = c(X = 1, Y = 1, Z = 1)
                    )

    out <- rxSolve(ode,
                   params = c(a = -8 / 3, b = -10, c = 28),
                   events = et, inits = c(X = 1, Y = 1, Z = 1),
                   drop = "X"
                   )

    expect_equal(names(out), c("time", "Y", "Z"))
    expect_equal(out$time, out0$time)
    expect_equal(out$Y, out0$Y)
    expect_equal(out$Z, out0$Z)

    out <- rxSolve(ode,
                   params = c(a = -8 / 3, b = -10, c = 28),
                   events = et, inits = c(X = 1, Y = 1, Z = 1),
                   drop = c("X", "Y")
                   )

    expect_equal(names(out), c("time", "Z"))
    expect_equal(out$time, out0$time)
    expect_equal(out$Z, out0$Z)


    expect_warning(rxSolve(ode,
                           params = c(a = -8 / 3, b = -10, c = 28),
                           events = et, inits = c(X = 1, Y = 1, Z = 1),
                           drop = c("X", "Y", "ww")
                           ))

    expect_warning(rxSolve(ode,
                           params = c(a = -8 / 3, b = -10, c = 28),
                           events = et, inits = c(X = 1, Y = 1, Z = 1),
                           drop = c("X", "Y", "ww"), warnDrop = FALSE
                           ), NA)

    expect_warning(rxSolve(ode,
                           params = c(a = -8 / 3, b = -10, c = 28),
                           events = et, inits = c(X = 1, Y = 1, Z = 1),
                           drop = "time"
                           ))
  })
})