middle-row mc segments: 2 (expect 2)
all-spanned segments: 0 (expect 0)
no-mc segments: 1 (expect 1)
edge+dashed segments: 3 (expect 3: left full, middle 1, right full)
matrix cols: 3 (expect 3)
mc node: {"type":"multicolumn","n":3,"align":"c","borders":[0,0]}
pmatrix MathML columnspan/align: true true
error ok: outside env -> KaTeX parse error: \multicolumn valid only within array environment at position 
error ok: in plain math -> KaTeX parse error: \multicolumn valid only within array environment at position 
error ok: n=0 -> KaTeX parse error: Invalid column count for \multicolumn: 0 at position 19: …gin
error ok: n=-1 -> KaTeX parse error: Invalid column count for \multicolumn: -1 at position 19: …gi
error ok: n=1.5 -> KaTeX parse error: Invalid column count for \multicolumn: 1.5 at position 19: …g
error ok: n=x -> KaTeX parse error: Invalid column count for \multicolumn: x at position 19: …gin
error ok: n empty -> KaTeX parse error: Invalid column count for \multicolumn:  at position 19: …gin{
error ok: n exceeds total -> KaTeX parse error: \multicolumn spans 3 columns, but only 2 column(s) remain in 
error ok: n exceeds remaining -> KaTeX parse error: \multicolumn spans 3 columns, but only 2 column(s) remain in 
error ok: empty align -> KaTeX parse error: Invalid \multicolumn alignment:  at position 19: …gin{array}{
error ok: bad align char -> KaTeX parse error: Invalid \multicolumn alignment: x at position 19: …gin{array}
error ok: two align chars -> KaTeX parse error: Invalid \multicolumn alignment: lc at position 19: …gin{array
error ok: only | -> KaTeX parse error: Invalid \multicolumn alignment: | at position 19: …gin{array}
error ok: colon -> KaTeX parse error: Invalid \multicolumn alignment: c: at position 19: …gin{array
error ok: content before -> KaTeX parse error: \multicolumn must be the only content of a cell at position 4
error ok: content after -> KaTeX parse error: \multicolumn must be the only content of a cell at position 4
error ok: gathered -> KaTeX parse error: \multicolumn is not supported in the {gathered} environment a
error ok: pmatrix* -> KaTeX parse error: \multicolumn is not supported in the {pmatrix*} environment a
error ok: subarray -> KaTeX parse error: \multicolumn is not supported in the {subarray} environment a
error ok: darray -> KaTeX parse error: \multicolumn is not supported in the {darray} environment at 
error ok: dcases -> KaTeX parse error: \multicolumn is not supported in the {dcases} environment at 
build ok: \begin{array}{cc} \multicolumn{2}{c}{x} \\ a & b\end{array}
build ok: \begin{matrix} \multicolumn{2}{c}{x} \\ a & b\end{matrix}
build ok: \begin{pmatrix} \multicolumn{2}{c}{x} \\ a & b\end{pmatrix}
build ok: \begin{bmatrix} \multicolumn{2}{c}{x} \\ a & b\end{bmatrix}
build ok: \begin{Bmatrix} \multicolumn{2}{c}{x} \\ a & b\end{Bmatrix}
build ok: \begin{vmatrix} \multicolumn{2}{c}{x} \\ a & b\end{vmatrix}
build ok: \begin{Vmatrix} \multicolumn{2}{c}{x} \\ a & b\end{Vmatrix}
build ok: \begin{cases} \multicolumn{2}{c}{x} \\ a & b\end{cases}
build ok: \begin{rcases} \multicolumn{2}{c}{x} \\ a & b\end{rcases}
build ok: \begin{aligned} \multicolumn{2}{c}{x} \\ a &= b\end{aligned}
build ok: \begin{smallmatrix} \multicolumn{2}{c}{x} \\ a & b\end{small
build ok: \begin{array}{cc} \multicolumn{2}{|c|}{x} \\ a & b\end{array
build ok: \begin{array}{ccc} \multicolumn{2}{|l}{x} & y \\ a & b & c\e
build ok: \begin{array}{ccc} a & \multicolumn{2}{r|}{x} \\ a & b & c\e
build ok: \begin{array}{cc} \multicolumn{1}{r}{x} & y\end{array}
