rxTest({
  test_that("drop support functions", {
    expect_equal(.getModelLineEquivalentLhsExpression(quote(-cl)), quote(cl))
    expect_equal(.getModelLineEquivalentLhsExpression(quote(-lag(matt))), quote(lag(matt)))
    expect_equal(.getModelLineEquivalentLhsExpression(quote(-alag(matt))), quote(alag(matt)))
    expect_equal(.getModelLineEquivalentLhsExpression(quote(-F(matt))), quote(F(matt)))
    expect_equal(.getModelLineEquivalentLhsExpression(quote(-f(matt))), quote(f(matt)))
    expect_equal(.getModelLineEquivalentLhsExpression(quote(-rate(matt))), quote(rate(matt)))
    expect_equal(.getModelLineEquivalentLhsExpression(quote(-dur(matt))), quote(dur(matt)))
    expect_equal(.getModelLineEquivalentLhsExpression(quote(-matt(0))), quote(matt(0)))
    expect_equal(.getModelLineEquivalentLhsExpression(quote(-d/dt(matt))), quote(d/dt(matt)))
    expect_equal(.getModelLineEquivalentLhsExpression(quote(-cp ~ .)), quote(cp))

    expect_true(.isDropExpression(quote(-v)))
    expect_false(.isDropExpression(quote(-v+3)))
    expect_false(.isDropExpression(quote(-3)))

    expect_false(.isDropExpression(quote(x <- y)))
    expect_false(.isDropExpression(quote(x + y ~ c(1, 0.01, 1))))

    expect_true(.isDropExpression(quote(-f(depot))))
    expect_true(.isDropExpression(quote(-F(depot))))
    expect_true(.isDropExpression(quote(-alag(depot))))
    expect_true(.isDropExpression(quote(-lag(depot))))
    expect_true(.isDropExpression(quote(-rate(depot))))
    expect_true(.isDropExpression(quote(-dur(depot))))
    expect_false(.isDropExpression(quote(-matt(depot))))
    expect_false(.isDropExpression(quote(-f(depot + central))))

    expect_true(.isDropExpression(quote(-depot(0))))
    expect_true(.isDropExpression(quote(-d/dt(depot))))

    expect_true(.isDropExpression(quote(-cp~.)))
  })

  test_that("drop from model before single endpoint model", {
    one.compartment <- function() {
      ini({
        tka <- 0.45 ; label("Log Ka")
        tcl <- 1 ; label("Log Cl")
        tv <- 3.45 ; label("Log V")
        eta.ka ~ 0.6
        eta.cl ~ 0.3
        eta.v ~ 0.1
        add.err <- 0.7
      })
      model({
        ka <- exp(tka + eta.ka)
        cl <- exp(tcl + eta.cl)
        v <- exp(tv + eta.v)
        d / dt(depot) <- -ka * depot
        d / dt(center) <- ka * depot - cl / v * center
        f(depot) <- 3
        cp <- center / v
        cp2 <- cp * cl
        cp ~ add(add.err)
      })
    }

    f2 <- one.compartment %>% model(-cp2)

    expect_equal(f2$lstExpr[[8]], quote(cp ~ add(add.err)))
    expect_length(f2$lstExpr, 8L)
  })

  test_that("drop from model after single endpoint model", {
    one.compartment <- function() {
      ini({
        tka <- 0.45 ; label("Log Ka")
        tcl <- 1 ; label("Log Cl")
        tv <- 3.45 ; label("Log V")
        eta.ka ~ 0.6
        eta.cl ~ 0.3
        eta.v ~ 0.1
        add.err <- 0.7
      })
      model({
        ka <- exp(tka + eta.ka)
        cl <- exp(tcl + eta.cl)
        v <- exp(tv + eta.v)
        d / dt(depot) <- -ka * depot
        d / dt(center) <- ka * depot - cl / v * center
        f(depot) <- 3
        cp <- center / v
        cp ~ add(add.err)
        cp2 <- cp * cl
      })
    }

    f2 <- one.compartment %>% model(-cp2)
    expect_equal(f2$lstExpr[[8]], quote(cp ~ add(add.err)))
    expect_length(f2$lstExpr, 8L)
  })

  test_that("drop endpoint from  multiple endpoint model", {
    pk.turnover.emax <- function() {
      ini({
        tktr <- log(1)
        tka <- log(1)
        tcl <- log(0.1)
        tv <- log(10)
        ##
        eta.ktr ~ 1
        eta.ka ~ 1
        eta.cl ~ 2
        eta.v ~ 1
        prop.err <- 0.1
        pkadd.err <- 0.1
        ##
        temax <- logit(0.8)
        #temax <- 7.5
        tec50 <- log(0.5)
        tkout <- log(0.05)
        te0 <- log(100)
        ##
        eta.emax ~ .5
        eta.ec50  ~ .5
        eta.kout ~ .5
        eta.e0 ~ .5
        ##
        pdadd.err <- 10
      })
      model({
        ktr <- exp(tktr + eta.ktr)
        ka <- exp(tka + eta.ka)
        cl <- exp(tcl + eta.cl)
        v <- exp(tv + eta.v)
        ##
        #poplogit = log(temax/(1-temax))
        emax=expit(temax+eta.emax)
        #logit=temax+eta.emax
        ec50 =  exp(tec50 + eta.ec50)
        kout = exp(tkout + eta.kout)
        e0 = exp(te0 + eta.e0)
        ##
        DCP = center/v
        PD=1-emax*DCP/(ec50+DCP)
        ##
        effect(0) = e0
        kin = e0*kout
        ##
        d/dt(depot) = -ktr * depot
        d/dt(gut) =  ktr * depot -ka * gut
        d/dt(center) =  ka * gut - cl / v * center
        d/dt(effect) = kin*PD -kout*effect
        ##
        cp = center / v
        cp ~ prop(prop.err) + add(pkadd.err)
        effect ~ add(pdadd.err)
      })
    }

    suppressMessages(
      f2 <- pk.turnover.emax %>% model(-cp)
    )

    expect_length(f2$predDf$cond, 1)
    expect_equal(f2$predDf$cond, "effect")
    expect_length(f2$lstExpr, 17)
  })

  test_that("drop compartment and compartment-related properties", {
    one.compartment <- function() {
      ini({
        tka <- 0.45 ; label("Log Ka")
        tcl <- 1 ; label("Log Cl")
        tv <- 3.45 ; label("Log V")
        eta.ka ~ 0.6
        eta.cl ~ 0.3
        eta.v ~ 0.1
        add.err <- 0.7
      })
      model({
        ka <- exp(tka + eta.ka)
        cl <- exp(tcl + eta.cl)
        v <- exp(tv + eta.v)
        d/dt(depot) <- -ka * depot
        d/dt(center) <- ka * depot - cl / v * center
        f(depot) <- 3
        cp <- center / v
        cp ~ add(add.err)
        cp2 <- cp * cl
      })
    }

    suppressMessages(
      f2 <- one.compartment %>% model(-d/dt(depot))
    )
    expect_equal(f2$mv0$state, "center")
    expect_length(f2$lstExpr, 7L)

    f2 <- one.compartment %>% model(-f(depot))
    expect_equal(f2$mv0$state, c("depot", "center"))
    expect_length(f2$lstExpr, 8L)
  })

  test_that("drop endpoint test", {
    ocmt <- function() {
      ini({
        tka <- 0.45 ; label("Log Ka")
        tcl <- 1 ; label("Log Cl")
        tv <- 3.45 ; label("Log V")
        eta.ka ~ 0.6
        eta.cl ~ 0.3
        eta.v ~ 0.1
        add.err <- 0.7
      })
      model({
        ka <- exp(tka + eta.ka)
        cl <- exp(tcl + eta.cl)
        v <- exp(tv + eta.v)
        d/dt(depot) <- -ka * depot
        d/dt(center) <- ka * depot - cl / v * center
        f(depot) <- 3
        cp <- center / v
        cp ~ add(add.err)
      })
    }

    suppressMessages(
      f2 <- ocmt %>% model(-cp ~ .)
    )
    expect_true(is.null(f2$predDf))
    expect_equal(f2$theta, c(tka = 0.45, tcl = 1, tv = 3.45))

    suppressMessages(
      f3 <- f2 %>% model(cp ~ add(add.sd), append=TRUE)
    )

    expect_false(is.null(f3$predDf))
    expect_equal(f3$theta, c(tka = 0.45, tcl = 1, tv = 3.45, add.sd=1))
  })
})