context("is_tree") test_that("is_tree works for non-trees", { g <- make_graph("zachary") expect_false(is_tree(g)) expect_equal(is_tree(g, details=TRUE), list(res=FALSE, root=V(g)[numeric(0)])) g <- sample_pa(15, m=3) expect_false(is_tree(g)) expect_false(is_tree(g, details=TRUE)$res) }) test_that("is_tree works for undirected trees", { # g <- permute(make_tree(7, 2), c(5, 2, 3, 4, 1, 6, 7)) g <- make_tree(7, 2) expect_true(is_tree(g)) expect_equal(is_tree(g, details=TRUE), list(res=TRUE, root=V(g)[1])) }) test_that("is_tree works for directed in-trees", { g <- permute(make_tree(7, 2, mode="in"), c(5, 2, 3, 4, 1, 6, 7)) expect_true(is_tree(g, mode="in")) expect_equal(is_tree(g, mode="in", details=TRUE), list(res=TRUE, root=V(g)[5])) expect_true(is_tree(g, mode="all")) expect_equal(is_tree(g, mode="all", details=TRUE), list(res=TRUE, root=V(g)[1])) expect_false(is_tree(g, mode="out")) expect_false(is_tree(g, mode="out", details=TRUE)$res) }) test_that("is_tree works for directed out-trees", { g <- permute(make_tree(7, 2, mode="out"), c(3, 2, 1, 4, 5, 6, 7)) expect_true(is_tree(g, mode="out")) expect_equal(is_tree(g, mode="out", details=TRUE), list(res=TRUE, root=V(g)[3])) expect_true(is_tree(g, mode="all")) expect_equal(is_tree(g, mode="all", details=TRUE), list(res=TRUE, root=V(g)[1])) expect_false(is_tree(g, mode="in")) expect_false(is_tree(g, mode="in", details=TRUE)$res) }) test_that("the null graph is not a tree", { expect_false(is_tree(make_empty_graph(0))) }) test_that("a graph with a single vertex and no edges is tree", { expect_true(is_tree(make_empty_graph(1))) }) context("to_prufer, make_from_prufer") test_that("to_prufer and make_from_prufer works for trees", { g <- make_tree(13, 3, mode="undirected") seq <- to_prufer(g) g2 <- make_from_prufer(seq) expect_true(isomorphic(g, g2)) g <- make_tree(13, 3, mode="out") seq <- to_prufer(g) g2 <- make_from_prufer(seq) g3 <- as.undirected(g) expect_true(isomorphic(g2, g3)) g <- make_tree(13, 3, mode="in") seq <- to_prufer(g) g2 <- make_from_prufer(seq) g3 <- as.undirected(g) expect_true(isomorphic(g2, g3)) }) test_that("make_(from_prufer(...)) works", { g <- make_tree(13, 3, mode="undirected") seq <- to_prufer(g) g2 <- make_(from_prufer(seq)) expect_true(isomorphic(g, g2)) }) test_that("to_prufer prints an error for non-trees", { expect_error(to_prufer(make_graph("zachary")), "must be a tree") }) context("sample_tree") test_that("sample_tree works", { g <- sample_tree(100) expect_false(is_directed(g)) expect_that(ecount(g), equals(99)) expect_that(vcount(g), equals(100)) expect_true(is_tree(g)) g <- sample_tree(50, directed=T) expect_true(is_directed(g)) expect_that(ecount(g), equals(49)) expect_that(vcount(g), equals(50)) expect_true(is_tree(g)) g <- sample_tree(200, method="prufer") expect_false(is_directed(g)) expect_that(ecount(g), equals(199)) expect_that(vcount(g), equals(200)) expect_true(is_tree(g)) g <- sample_tree(200, method="lerw") expect_false(is_directed(g)) expect_that(ecount(g), equals(199)) expect_that(vcount(g), equals(200)) expect_true(is_tree(g)) }) test_that("sample_(tree(...)) works", { g <- sample_(tree(200, method="prufer")) expect_false(is_directed(g)) expect_that(ecount(g), equals(199)) expect_that(vcount(g), equals(200)) expect_true(is_tree(g)) g2 <- sample_(tree(200, method="prufer")) expect_false(is_directed(g2)) expect_that(ecount(g2), equals(199)) expect_that(vcount(g2), equals(200)) expect_true(is_tree(g2)) expect_false(identical_graphs(g, g2)) }) test_that("sample_tree yields a singleton graph for n=1", { g <- sample_tree(1) expect_false(is_directed(g)) expect_that(ecount(g), equals(0)) expect_that(vcount(g), equals(1)) expect_true(is_tree(g)) }) test_that("sample_tree yields a null graph for n=0", { g <- sample_tree(0) expect_false(is_directed(g)) expect_that(ecount(g), equals(0)) expect_that(vcount(g), equals(0)) expect_false(is_tree(g)) # edge case, the null graph is not a tree even though it was generated by sample_tree() }) test_that("sample_tree throws an error for the Prufer method with directed graphs", { expect_error(sample_tree(10, method="prufer", directed=T), "nvalid value") }) context("sample_spanning_tree") test_that("sample_spanning_tree works for connected graphs", { g <- make_full_graph(8) edges <- sample_spanning_tree(g) expect_that(length(edges), equals(7)) sg <- subgraph.edges(g, edges) expect_that(vcount(sg), equals(8)) expect_that(ecount(sg), equals(7)) expect_that(sg, is_tree) }) test_that("sample_spanning_tree works for disconnected graphs", { g <- make_full_graph(8) %du% make_full_graph(5) edges <- sample_spanning_tree(g, vid=8) sg <- subgraph.edges(g, edges, delete.vertices=TRUE) expect_that(vcount(sg), equals(8)) expect_that(ecount(sg), equals(7)) expect_that(sg, is_tree) edges <- sample_spanning_tree(g, vid=9) sg <- subgraph.edges(g, edges, delete.vertices=TRUE) expect_that(vcount(sg), equals(5)) expect_that(ecount(sg), equals(4)) expect_that(sg, is_tree) edges <- sample_spanning_tree(g) sg <- subgraph.edges(g, edges, delete.vertices=FALSE) expect_that(vcount(sg), equals(13)) expect_that(ecount(sg), equals(11)) expect_that(induced_subgraph(sg, 1:8), is_tree) expect_that(induced_subgraph(sg, 9:13), is_tree) })
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