No vertices, no allowed starting vertex ID.

Null graph without explicit start vertex:
result: NaN, from -1 to -1

1 vertex:
result: 0, from 0 to 0

2 vertices unconn = true:
result: 0, from 0 to 0

2 vertices unconn = false:
result: Inf, from -1 to -1

2 vertices, directed, unconn = true:
result: 0, from 0 to 0

2 vertices, directed, unconn = false:
result: Inf, from -1 to -1

Undirected disconnected graph with loops and multiple edges.
result: 3, from 0 to 4

result: 3, from 4 to 0

result: 3, from 4 to 0

result: 3, from 0 to 4

result: 3, from 4 to 0

result: 0, from 5 to 5

Directed disconnected graph with loops and multiple edges, direction ignored.
result: 3, from 0 to 4

result: 3, from 4 to 0

result: 3, from 4 to 0

result: 3, from 0 to 4

result: 3, from 4 to 0

result: 0, from 5 to 5

Directed disconnected graph with loops and multiple edges.
result: 3, from 0 to 4

result: 2, from 2 to 1

result: 3, from 0 to 4

result: 3, from 0 to 4

result: 3, from 0 to 4

result: 0, from 5 to 5

Directed graph, pointing outward from 2.
result: 2, from 2 to 0

result: 2, from 2 to 0

result: 2, from 2 to 0

result: 2, from 2 to 0

result: 2, from 2 to 4

Same graph, direction ignored.
result: 4, from 0 to 4

result: 4, from 4 to 0

result: 4, from 0 to 4

result: 4, from 0 to 4

result: 4, from 4 to 0

Same graph, unconn = false.
result: Inf, from -1 to -1

Same graph, undirected.
result: 4, from 0 to 4

result: 4, from 4 to 0

result: 4, from 0 to 4

result: 4, from 0 to 4

result: 4, from 4 to 0

Petersen graph with random starts.
result: 2, from 1 to 4

result: 2, from 5 to 1

result: 2, from 8 to 2

result: 2, from 9 to 0

result: 2, from 9 to 0

result: 2, from 7 to 1

