test_that("complete_dates works", {
    dat <- data.frame(
        dates = Sys.Date() + 1:4,
        groups1 = rep(c("bob","george"), 2),
        groups2 = c(rep("groupa", 2), rep("groupb", 2)),
        counts1 = 1:4,
        counts2 = 11:14
    )

    i <- incidence(
        dat,
        date_index = "dates",
        groups = c("groups1", "groups2"),
        counts = c("counts1", "counts2")
    )

    res <- complete_dates(i, fill = NA)
    expect_identical(nrow(res), 32L)
    tmp <- res[complete.cases(res),]
    row.names(tmp) <- NULL
    expect_identical(tmp, i)
    res2 <- complete_dates(i)
    expect_identical(sum(res2$counts1), sum(i$counts1))
    expect_identical(sum(res2$counts2), sum(i$counts2))
    expect_identical(nrow(res2), 32L)
})