Fix class of date attributes author-network test

As of igraph version 1.4.0, the classes of edge attributes are respected in
igraph. Therefore, dates in the expected outcomes of our tests need to be of
class `POSIXct`. As the `I()` operator prevents an automatic conversion, we need
to manually convert the dates to the correct class. However, as `I()` adds the
`AsIs` class, we need to remove this class from the affected edge attributes
again, as otherwise the expected network and the built network would not be
equal.

To make this test succeed in both, igraph versions < 1.4.0 and igraph versions
>= 1.4.0, the expected class is derived from the class of the date attribute in
the built network. This way, the test is able to pass independent of the used
igraph version.

This fix addresses se-sic#236.

Signed-off-by: Christian Hechtl <hechtl@cs.uni-saarland.de>
Signed-off-by: Thomas Bock <bockthom@cs.uni-saarland.de>

tests/test-networks-author.R

@@ -13,9 +13,11 @@
 ##
 ## Copyright 2017, 2019 by Claus Hunsen <hunsen@fim.uni-passau.de>
 ## Copyright 2017 by Christian Hechtl <hechtl@fim.uni-passau.de>
+## Copyright 2023 by Christian Hechtl <hechtl@cs.uni-saarland.de>
 ## Copyright 2017 by Felix Prasse <prassefe@fim.uni-passau.de>
 ## Copyright 2018 by Barbara Eckl <ecklbarb@fim.uni-passau.de>
 ## Copyright 2018 by Thomas Bock <bockthom@fim.uni-passau.de>
+## Copyright 2023 by Thomas Bock <bockthom@cs.uni-saarland.de>
 ## Copyright 2018 by Jakob Kronawitter <kronawij@fim.uni-passau.de>
 ## Copyright 2018-2019 by Anselm Fehnker <fehnker@fim.uni-passau.de>
 ## Copyright 2021 by Johannes Hostert <s8johost@stud.uni-saarland.de>
@@ -421,12 +423,19 @@ test_that("Network construction of the undirected simplified author-cochange net
                          kind = TYPE.AUTHOR,
                          type = TYPE.AUTHOR)
 
+    ## make test independent of igraph version
+    date.attr = igraph::get.edge.attribute(network.built, "date")
+    date.conversion.function = ifelse(all(sapply(date.attr, lubridate::is.POSIXct)),
+                                      get.date.from.unix.timestamp, identity)
+
     ## edge attributes
     data = data.frame(
         from = c("Björn", "Olaf", "Olaf", "Karl"),
         to = c("Olaf", "Karl", "Thomas", "Thomas"),
-        date = I(list(c(1468339139, 1468339245), c(1468339541, 1468339570), c(1468339541, 1468339592),
-                      c(1468339570, 1468339592))),
+        date = I(list(date.conversion.function(c(1468339139, 1468339245)),
+                      date.conversion.function(c(1468339541, 1468339570)),
+                      date.conversion.function(c(1468339541, 1468339592)),
+                      date.conversion.function(c(1468339570, 1468339592)))),
         artifact.type = I(list(c("Feature", "Feature"), c("Feature", "Feature"), c("Feature", "Feature"),
                                c("Feature", "Feature"))),
         hash = I(list(
@@ -442,6 +451,13 @@ test_that("Network construction of the undirected simplified author-cochange net
         relation = "cochange"
     )
 
+    ## remove the 'AsIs' class from the edge attributes that have been inserted via `I(...)`
+    data[["date"]] = unclass(data[["date"]])
+    data[["artifact.type"]] = unclass(data[["artifact.type"]])
+    data[["hash"]] = unclass(data[["hash"]])
+    data[["file"]] = unclass(data[["file"]])
+    data[["artifact"]] = unclass(data[["artifact"]])
+
     ## build expected network
     network.expected = igraph::graph.data.frame(data, directed = FALSE, vertices = authors)