test_that("compare_observations detects value differences", {
  df1 <- data.frame(a = c(1, 2, 3), b = c("x", "y", "z"), stringsAsFactors = FALSE)
  df2 <- data.frame(a = c(1, 5, 3), b = c("x", "y", "w"), stringsAsFactors = FALSE)
  result <- compare_observations(df1, df2)
  expect_equal(result$discrepancies[["a"]], 1)
  expect_equal(result$discrepancies[["b"]], 1)
})

test_that("compare_observations works with identical data", {
  df <- data.frame(a = 1:3, b = letters[1:3], stringsAsFactors = FALSE)
  result <- compare_observations(df, df)
  expect_true(all(result$discrepancies == 0))
  expect_equal(length(result$details), 0)
})

test_that("compare_observations handles factors", {
  df1 <- data.frame(a = factor(c("x", "y")), stringsAsFactors = TRUE)
  df2 <- data.frame(a = factor(c("x", "z")), stringsAsFactors = TRUE)
  result <- compare_observations(df1, df2)
  expect_equal(result$discrepancies[["a"]], 1)
})

test_that("compare_observations errors on mismatched rows", {
  df1 <- data.frame(a = 1:3)
  df2 <- data.frame(a = 1:5)
  expect_error(compare_observations(df1, df2), "different numbers of rows")
})

test_that("compare_observations shows row details", {
  df1 <- data.frame(a = c(1, 2, 3))
  df2 <- data.frame(a = c(1, 9, 3))
  result <- compare_observations(df1, df2)
  expect_true("a" %in% names(result$details))
  expect_equal(result$details$a$Row, 2)
  expect_equal(result$details$a$Value_in_df1, 2)
  expect_equal(result$details$a$Value_in_df2, 9)
})