Error in `eval(code, test_env)`: object 'Cd2' not found

ls <- list(time = 1:3, Nsurv = 10:8, replicate = "A", conc = 2.0)
df <- data.frame(time = 1:3, Nsurv = 10:8, replicate = "A", conc = 2.0)
df_shorter <- Cd2[, c("time", "conc", "replicate")]
df_longer <- Cd2 ; df_longer$ADD = "add"
df_missing <- df_shorter ; df_missing$ADD = "add"
test_that("time is (1) numeric, (2) unique, (3) minimal value is 0.s", {
df_no_numeric <- Cd2 ; df_no_numeric$time = as.character(df_no_numeric$time)
df_no_unique <- Cd2 ; df_no_unique$time[1:3] = df_no_unique$time[3]
df_no_min0 <- Cd2 ; df_no_min0[df_no_min0$time == 0, ]$time[1] = 1
df_no_numeric <- Cd2 ; df_no_numeric$conc = as.character(df_no_numeric$conc)
test_that("Nsurv contains integer and positive >=0", {
df_no_intNsurv <- Cd2 ; df_no_intNsurv$Nsurv[10] = df_no_intNsurv$Nsurv[10] + 0.2
df_no_posNsurv <- Cd2 ; df_no_posNsurv$Nsurv[10] = -10
test_that("Nsurv never decreases with time and > 0 at 0", {
df_Nurv0_at_time0[df_Nurv0_at_time0$time == 0, ]$Nsurv[1] = 0
df_Nurv_increase$Nsurv[2] = df_Nurv_increase$Nsurv[1] + 2
test_that("each (replicate, time) pair is unique", {
test_that("'Nrepro' must contain only positive (>=0) integer values.", {
df_no_intNrepro <- Cd2 ; df_no_intNrepro$Nrepro[10] = df_no_intNrepro$Nrepro[10] + 0.2
df_no_posNrepro <- Cd2 ; df_no_posNrepro$Nrepro[10] = -10
test_that("each time T for which Nsurv = 0, Nrepro = 0 at time T+1.", {
df_Nsurv0 <- Cd2[Cd2$replicate == "19", ]
df_Nsurv0[df_Nsurv0$Nsurv == 0, ]$Nrepro[2] = 10

"time is (1) numeric, (2) unique, (3) minimal value is 0.s"
"Nsurv contains integer and positive >=0"
"Nsurv never decreases with time and > 0 at 0"
"'Nrepro' must contain only positive (>=0) integer values."
"each time T for which Nsurv = 0, Nrepro = 0 at time T+1."

time is (1) numeric, (2) unique, (3) minimal value is 0.s

Nsurv never decreases with time and > 0 at 0

'Nrepro' must contain only positive (>=0) integer values.

each time T for which Nsurv = 0, Nrepro = 0 at time T+1.

Error in `gzfile(file, "rb")`: cannot open the connection