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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