tests/testthat/test-cycles.R

In igraph/rigraph: Network Analysis and Visualization

test_that("find_cycle() works", {
  g <- make_graph(c(1, 2, 2, 3, 1, 3, 1, 1), directed = TRUE)

  cycle <- find_cycle(g)
  expect_equal(length(cycle$vertices), 1)
  expect_equal(length(cycle$edges), 1)

  # Finding a cycle of length 1 or 3 are both valid here
  cycle <- find_cycle(g, mode = "all")
  expect_equal(length(cycle$vertices), 3)
  expect_equal(length(cycle$edges), 3)
})

test_that("simple_cycle() works directed", {
  g <- graph_from_literal(A -+ B -+ C -+ A -+ D -+ E +- F -+ A, E -+ E, A -+ F, simplify = FALSE)
  all_simple_cycles <- simple_cycles(g)
  expect_length(all_simple_cycles$vertices, 3)
  expect_length(all_simple_cycles$edges, 3)
  true_length <- list(vertices = c(3, 2, 1), edges = c(3, 2, 1))

  for (i in 1:3) {
    expect_length(all_simple_cycles$vertices[[i]], true_length$vertices[[i]])
    expect_length(all_simple_cycles$edges[[i]], true_length$edges[[i]])
  }

  expect_equal(as.numeric(all_simple_cycles$vertices[[1]]), 1:3)
})

test_that("simple_cycle() works undirected", {
  g <- graph_from_literal(A -+ B -+ C -+ A -+ D -+ E +- F -+ A, E -+ E, A -+ F, simplify = FALSE)
  all_simple_cycles <- simple_cycles(g, mode = "all")
  expect_length(all_simple_cycles$vertices, 5)
  expect_length(all_simple_cycles$edges, 5)

  true_length <- list(vertices = c(3, 4, 4, 2, 1), edges = c(3, 4, 4, 2, 1))
  for (i in 1:5) {
    expect_length(all_simple_cycles$vertices[[i]], true_length$vertices[[i]])
    expect_length(all_simple_cycles$edges[[i]], true_length$edges[[i]])
  }
  expect_equal(as.numeric(all_simple_cycles$vertices[[2]]), c(1, 4, 5, 6))

  all_simple_cycles_23 <- simple_cycles(g, mode = "all", min = 2, max = 3)
  expect_length(all_simple_cycles$vertices, 5)
  expect_length(all_simple_cycles$edges, 5)
})