test_that("make_graph works", {
  g <- make_graph(1:10)
  g2 <- make_empty_graph(n = 10) + edges(1:10)
  expect_true(identical_graphs(g, g2))
})

test_that("make_graph accepts an empty vector or NULL", {
  g <- make_graph(c())
  g2 <- make_empty_graph(n = 0)
  expect_true(identical_graphs(g, g2))

  g <- make_graph(NULL, n = 0)
  expect_true(identical_graphs(g, g2))

  g <- make_graph(edges = c(), n = 0)
  expect_true(identical_graphs(g, g2))
})

test_that("make_graph works for numeric edges and isolates", {
  g <- make_graph(1:10, n = 20)
  g2 <- make_empty_graph(n = 20) + edges(1:10)
  expect_true(identical_graphs(g, g2))
})

test_that("make_graph handles names", {
  g <- make_graph(letters[1:10])
  g2 <- make_empty_graph() + vertices(letters[1:10]) + edges(letters[1:10])
  expect_true(identical_graphs(g, g2))
})

test_that("make_graph handles names and isolates", {
  g <- make_graph(letters[1:10], isolates = letters[11:20])
  g2 <- make_empty_graph() + vertices(letters[1:20]) + edges(letters[1:10])
  expect_true(identical_graphs(g, g2))
})

test_that("make_graph gives warning for ignored arguments", {
  expect_warning(
    make_graph(letters[1:10], n = 10)
  )

  expect_warning(
    make_graph(1:10, isolates = 11:12)
  )
})

test_that("a make_graph bug is fixed", {
  E <- cbind(1, 3)
  d <- 3
  g <- make_graph(as.vector(t(E)), d, FALSE)

  expect_equal(vcount(g), 3)
  expect_equal(ecount(g), 1)
})

test_that("make_empty_graph gives an error for invalid arguments", {
  expect_error(make_empty_graph(NULL))
  expect_warning(expect_error(make_empty_graph("spam")))
})