diff --git a/tests/contact-chain.R b/tests/contact-chain.R
index 4426257..d98f54a 100644
--- a/tests/contact-chain.R
+++ b/tests/contact-chain.R
@@ -34,10 +34,10 @@ movements <- structure(list(source = 1:7, destination = c(4L, 5L, 5L,
 "t"), class = "data.frame", row.names = c(NA, -7L))
 ct <- Trace(movements,
             root = 8L,
-            inBegin = as.Date('2010-08-22'),
-            inEnd = as.Date('2010-10-01'),
-            outBegin = as.Date('2010-08-01'),
-            outEnd = as.Date('2010-08-31'))
+            inBegin = as.Date("2010-08-22"),
+            inEnd = as.Date("2010-10-01"),
+            outBegin = as.Date("2010-08-01"),
+            outEnd = as.Date("2010-08-31"))
 ct
 stopifnot(identical(IngoingContactChain(ct)$ingoingContactChain, 7L))
 stopifnot(identical(OutgoingContactChain(ct)$outgoingContactChain, 0L))
@@ -54,10 +54,10 @@ NA_integer_)), .Names = c("source", "destination", "t", "individual",
 "n"), row.names = c(NA, -4L), class = "data.frame")
 ct <- Trace(movements,
             root = 4L,
-            inBegin = as.Date('2010-07-22'),
-            inEnd = as.Date('2010-08-21'),
-            outBegin = as.Date('2010-08-01'),
-            outEnd = as.Date('2010-08-31'))
+            inBegin = as.Date("2010-07-22"),
+            inEnd = as.Date("2010-08-21"),
+            outBegin = as.Date("2010-08-01"),
+            outEnd = as.Date("2010-08-31"))
 ct
 stopifnot(identical(IngoingContactChain(ct)$ingoingContactChain, 3L))
 stopifnot(identical(OutgoingContactChain(ct)$outgoingContactChain, 0L))
@@ -73,10 +73,10 @@ c(NA_character_, NA_character_ ), n = c(NA_integer_, NA_integer_)),
 = c(NA, -2L), class = "data.frame")
 ct <- Trace(movements,
             root = 1L,
-            inBegin = as.Date('2010-08-02'),
-            inEnd = as.Date('2010-09-01'),
-            outBegin = as.Date('2010-09-01'),
-            outEnd = as.Date('2010-10-01'))
+            inBegin = as.Date("2010-08-02"),
+            inEnd = as.Date("2010-09-01"),
+            outBegin = as.Date("2010-09-01"),
+            outEnd = as.Date("2010-10-01"))
 ct
 stopifnot(identical(IngoingContactChain(ct)$ingoingContactChain, 1L))
 stopifnot(identical(OutgoingContactChain(ct)$outgoingContactChain, 0L))
@@ -95,10 +95,10 @@ NA_integer_)), .Names = c("source", "destination", "t", "individual",
 "n"), row.names = c(NA, -7L ), class = "data.frame")
 ct <- Trace(movements,
             root = 1L,
-            inBegin = as.Date('2010-08-02'),
-            inEnd = as.Date('2010-09-01'),
-            outBegin = as.Date('2010-08-01'),
-            outEnd = as.Date('2010-11-09'))
+            inBegin = as.Date("2010-08-02"),
+            inEnd = as.Date("2010-09-01"),
+            outBegin = as.Date("2010-08-01"),
+            outEnd = as.Date("2010-11-09"))
 ct
 stopifnot(identical(IngoingContactChain(ct)$ingoingContactChain, 0L))
 stopifnot(identical(OutgoingContactChain(ct)$outgoingContactChain, 7L))
@@ -114,10 +114,10 @@ c(NA_character_, NA_character_ ), n = c(NA_integer_, NA_integer_)),
 = c(NA, -2L), class = "data.frame")
 ct <- Trace(movements,
             root = 1L,
-            inBegin = as.Date('2010-07-02'),
-            inEnd = as.Date('2010-08-01'),
-            outBegin = as.Date('2010-08-01'),
-            outEnd = as.Date('2010-08-31'))
+            inBegin = as.Date("2010-07-02"),
+            inEnd = as.Date("2010-08-01"),
+            outBegin = as.Date("2010-08-01"),
+            outEnd = as.Date("2010-08-31"))
 ct
 stopifnot(identical(IngoingContactChain(ct)$ingoingContactChain, 0L))
 stopifnot(identical(OutgoingContactChain(ct)$outgoingContactChain, 1L))
@@ -134,10 +134,10 @@ class = "factor")), .Names = c("source", "destination", "t"), class =
 "data.frame", row.names = c(NA, -7L))
 ct <- Trace(movements,
             root = 1L,
-            inBegin = as.Date('2010-10-10'),
-            inEnd = as.Date('2010-10-20'),
-            outBegin = as.Date('2010-10-10'),
-            outEnd = as.Date('2010-10-20'))
+            inBegin = as.Date("2010-10-10"),
+            inEnd = as.Date("2010-10-20"),
+            outBegin = as.Date("2010-10-10"),
+            outEnd = as.Date("2010-10-20"))
 ct
 stopifnot(identical(IngoingContactChain(ct)$ingoingContactChain, 0L))
 stopifnot(identical(OutgoingContactChain(ct)$outgoingContactChain, 2L))
diff --git a/tests/degree.R b/tests/degree.R
index d26b2f1..45b0789 100644
--- a/tests/degree.R
+++ b/tests/degree.R
@@ -37,10 +37,10 @@ movements <- structure(list(source = c(1L, 2L, 3L, 3L),
 
 ct <- Trace(movements,
             root = 4L,
-            inBegin = as.Date('2010-08-02'),
-            inEnd = as.Date('2010-09-01'),
-            outBegin = as.Date('2010-08-01'),
-            outEnd = as.Date('2010-08-31'))
+            inBegin = as.Date("2010-08-02"),
+            inEnd = as.Date("2010-09-01"),
+            outBegin = as.Date("2010-08-01"),
+            outEnd = as.Date("2010-08-31"))
 
 stopifnot(identical(InDegree(ct)$inDegree, 1L))
 stopifnot(identical(OutDegree(ct)$outDegree, 0L))
@@ -56,7 +56,7 @@ movements <- structure(list(source = c(1L, 2L, 3L, 3L),
                        .Names = c("source", "destination", "t", "individual", "n"),
                        row.names = c(NA, -4L), class = "data.frame")
 
-ns <- NetworkSummary(movements, root = 4, tEnd = '2010-09-01', days = 30)
+ns <- NetworkSummary(movements, root = 4, tEnd = "2010-09-01", days = 30)
 stopifnot(identical(ns$inDegree, 1L))
 
 ##
@@ -70,7 +70,7 @@ movements <- structure(list(source = c(1L, 2L, 3L, 3L),
                        .Names = c("source", "destination", "t", "individual", "n"),
                        row.names = c(NA, -4L), class = "data.frame")
 
-ns <- NetworkSummary(movements, root = 4, tEnd = '2010-08-31', days = 30)
+ns <- NetworkSummary(movements, root = 4, tEnd = "2010-08-31", days = 30)
 stopifnot(identical(ns$outDegree, 0L))
 
 ##
@@ -86,10 +86,10 @@ movements <- structure(list(source = c(1L, 2L, 3L, 3L),
 
 ct <- Trace(movements,
             root = 4L,
-            inBegin = as.Date('2010-08-27'),
-            inEnd = as.Date('2010-09-01'),
-            outBegin = as.Date('2010-08-01'),
-            outEnd = as.Date('2010-08-31'))
+            inBegin = as.Date("2010-08-27"),
+            inEnd = as.Date("2010-09-01"),
+            outBegin = as.Date("2010-08-01"),
+            outEnd = as.Date("2010-08-31"))
 
 stopifnot(identical(InDegree(ct)$inDegree, 0L))
 stopifnot(identical(OutDegree(ct)$outDegree, 0L))
@@ -105,7 +105,7 @@ movements <- structure(list(source = c(1L, 2L, 3L, 3L),
                        .Names = c("source", "destination", "t", "individual", "n"),
                        row.names = c(NA, -4L), class = "data.frame")
 
-ns <- NetworkSummary(movements, root = 4, tEnd = '2010-09-01', days = 5)
+ns <- NetworkSummary(movements, root = 4, tEnd = "2010-09-01", days = 5)
 stopifnot(identical(ns$inDegree, 0L))
 
 ##
@@ -119,7 +119,7 @@ movements <- structure(list(source = c(1L, 2L, 3L, 3L),
                        .Names = c("source", "destination", "t", "individual", "n"),
                        row.names = c(NA, -4L), class = "data.frame")
 
-ns <- NetworkSummary(movements, root = 4, tEnd = '2010-08-31', days = 30)
+ns <- NetworkSummary(movements, root = 4, tEnd = "2010-08-31", days = 30)
 stopifnot(identical(ns$outDegree, 0L))
 
 ##
@@ -135,10 +135,10 @@ movements <- structure(list(source = c("1", "1", "1"),
 
 ct <- Trace(movements,
             root = 1L,
-            inBegin = as.Date('2010-08-02'),
-            inEnd = as.Date('2010-09-01'),
-            outBegin = as.Date('2010-08-01'),
-            outEnd = as.Date('2010-08-31'))
+            inBegin = as.Date("2010-08-02"),
+            inEnd = as.Date("2010-09-01"),
+            outBegin = as.Date("2010-08-01"),
+            outEnd = as.Date("2010-08-31"))
 
 stopifnot(identical(InDegree(ct)$inDegree, 0L))
 stopifnot(identical(OutDegree(ct)$outDegree, 3L))
@@ -154,7 +154,7 @@ movements <- structure(list(source = c("1", "1", "1"),
                        .Names = c("source", "destination", "t", "individual", "n"),
                        row.names = c(NA, -3L), class = "data.frame")
 
-ns <- NetworkSummary(movements, root = 1, tEnd = '2010-09-01', days = 30)
+ns <- NetworkSummary(movements, root = 1, tEnd = "2010-09-01", days = 30)
 stopifnot(identical(ns$inDegree,0L))
 
 ##
@@ -168,7 +168,7 @@ movements <- structure(list(source = c("1", "1", "1"),
                        .Names = c("source", "destination", "t", "individual", "n"),
                        row.names = c(NA, -3L), class = "data.frame")
 
-ns <- NetworkSummary(movements, root = 1, tEnd = '2010-08-31', days = 30)
+ns <- NetworkSummary(movements, root = 1, tEnd = "2010-08-31", days = 30)
 stopifnot(identical(ns$outDegree, 3L))
 
 ##
@@ -184,10 +184,10 @@ movements <- structure(list(source = c("1", "1", "1"),
 
 ct <- Trace(movements,
             root = 1L,
-            inBegin = as.Date('2010-08-02'),
-            inEnd = as.Date('2010-09-01'),
-            outBegin = as.Date('2010-08-01'),
-            outEnd = as.Date('2010-08-16'))
+            inBegin = as.Date("2010-08-02"),
+            inEnd = as.Date("2010-09-01"),
+            outBegin = as.Date("2010-08-01"),
+            outEnd = as.Date("2010-08-16"))
 
 stopifnot(identical(InDegree(ct)$inDegree, 0L))
 stopifnot(identical(OutDegree(ct)$outDegree, 2L))
@@ -203,7 +203,7 @@ movements <- structure(list(source = c("1", "1", "1"),
                        .Names = c("source", "destination", "t", "individual", "n"),
                        row.names = c(NA, -3L), class = "data.frame")
 
-ns <- NetworkSummary(movements, root = 1, tEnd = '2010-09-01', days = 30)
+ns <- NetworkSummary(movements, root = 1, tEnd = "2010-09-01", days = 30)
 stopifnot(identical(ns$inDegree, 0L))
 
 ##
@@ -217,5 +217,5 @@ movements <- structure(list(source = c("1", "1", "1"),
                        .Names = c("source", "destination", "t", "individual", "n"),
                        row.names = c(NA, -3L), class = "data.frame")
 
-ns <- NetworkSummary(movements, root = 1, tEnd = '2010-08-16', days = 15)
+ns <- NetworkSummary(movements, root = 1, tEnd = "2010-08-16", days = 15)
 stopifnot(identical(ns$outDegree, 2L))
diff --git a/tests/misc.R b/tests/misc.R
index 7511f38..7ee2f33 100644
--- a/tests/misc.R
+++ b/tests/misc.R
@@ -29,34 +29,34 @@ library(EpiContactTrace)
 ##
 movements <- data.frame(source = c(2L, 2L),
                         destination = c(1L, 2L),
-                        t = as.Date(c('2010-10-03', '2010-10-02')))
+                        t = as.Date(c("2010-10-03", "2010-10-02")))
 
 ct <- Trace(movements,
             root = 1L,
-            inBegin = as.Date('2010-09-30'),
-            inEnd = as.Date('2010-10-05'),
-            outBegin = as.Date('2010-10-05'),
-            outEnd = as.Date('2010-10-10'))
+            inBegin = as.Date("2010-09-30"),
+            inEnd = as.Date("2010-10-05"),
+            outBegin = as.Date("2010-10-05"),
+            outEnd = as.Date("2010-10-10"))
 
-stopifnot(identical(ct@ingoingContacts@source, '2'))
-stopifnot(identical(ct@ingoingContacts@destination, '1'))
+stopifnot(identical(ct@ingoingContacts@source, "2"))
+stopifnot(identical(ct@ingoingContacts@destination, "1"))
 
 ##
 ## Loops: Case 2
 ##
 movements <- data.frame(source = c(2L, 2L),
                         destination = c(1L, 2L),
-                        t = as.Date(c('2010-10-03', '2010-10-02')))
+                        t = as.Date(c("2010-10-03", "2010-10-02")))
 
 ct <- Trace(movements,
             root = 2L,
-            inBegin = as.Date('2010-09-30'),
-            inEnd = as.Date('2010-10-05'),
-            outBegin = as.Date('2010-09-30'),
-            outEnd = as.Date('2010-10-10'))
+            inBegin = as.Date("2010-09-30"),
+            inEnd = as.Date("2010-10-05"),
+            outBegin = as.Date("2010-09-30"),
+            outEnd = as.Date("2010-10-10"))
 
-stopifnot(identical(ct@outgoingContacts@source, '2'))
-stopifnot(identical(ct@outgoingContacts@destination, '1'))
+stopifnot(identical(ct@outgoingContacts@source, "2"))
+stopifnot(identical(ct@outgoingContacts@destination, "1"))
 
 ##
 ## Direction: Case 1
@@ -70,13 +70,13 @@ movements <- structure(list(source = 1:7,
 
 ct <- Trace(movements,
             root = 4L,
-            inBegin = as.Date('2010-08-02'),
-            inEnd = as.Date('2010-09-01'),
-            outBegin =  as.Date('2010-08-01'),
-            outEnd = as.Date('2010-08-31'))
+            inBegin = as.Date("2010-08-02"),
+            inEnd = as.Date("2010-09-01"),
+            outBegin =  as.Date("2010-08-01"),
+            outEnd = as.Date("2010-08-31"))
 
-stopifnot(identical(ct@ingoingContacts@direction, 'in'))
-stopifnot(identical(ct@outgoingContacts@direction, 'out'))
+stopifnot(identical(ct@ingoingContacts@direction, "in"))
+stopifnot(identical(ct@outgoingContacts@direction, "out"))
 
 ##
 ## Direction: Case 2
@@ -92,13 +92,13 @@ movements <- structure(list(source = c(1L, 2L, 3L, 3L),
 
 ct <- Trace(movements,
             root = 4L,
-            inBegin = as.Date('2010-08-02'),
-            inEnd = as.Date('2010-09-01'),
-            outBegin =  as.Date('2010-08-01'),
-            outEnd = as.Date('2010-08-31'))
+            inBegin = as.Date("2010-08-02"),
+            inEnd = as.Date("2010-09-01"),
+            outBegin =  as.Date("2010-08-01"),
+            outEnd = as.Date("2010-08-31"))
 
-stopifnot(identical(ct@ingoingContacts@direction, 'in'))
-stopifnot(identical(ct@outgoingContacts@direction, 'out'))
+stopifnot(identical(ct@ingoingContacts@direction, "in"))
+stopifnot(identical(ct@outgoingContacts@direction, "out"))
 
 ##
 ## Root not in movements: Case 1
@@ -114,10 +114,10 @@ movements <- structure(list(source = c("1", "1", "1"),
 
 ct <- Trace(movements,
             root = 15L,
-            inBegin = as.Date('2010-08-02'),
-            inEnd = as.Date('2010-09-01'),
-            outBegin = as.Date('2010-08-01'),
-            outEnd = as.Date('2010-08-31'))
+            inBegin = as.Date("2010-08-02"),
+            inEnd = as.Date("2010-09-01"),
+            outBegin = as.Date("2010-08-01"),
+            outEnd = as.Date("2010-08-31"))
 
 stopifnot(identical(InDegree(ct)$inDegree, 0L))
 stopifnot(identical(OutDegree(ct)$outDegree, 0L))
@@ -134,7 +134,7 @@ movements <- structure(list(source = c("1", "1", "1"),
                        .Names = c("source", "destination", "t", "individual", "n"),
                        row.names = c(NA, -3L), class = "data.frame")
 
-ns <- NetworkSummary(movements, root = 15, tEnd = '2010-09-01', days = 30)
+ns <- NetworkSummary(movements, root = 15, tEnd = "2010-09-01", days = 30)
 stopifnot(identical(ns$inDegree, 0L))
 
 ##
@@ -149,7 +149,7 @@ movements <- structure(list(source = c("1", "1", "1"),
                        .Names = c("source", "destination", "t", "individual", "n"),
                        row.names = c(NA, -3L), class = "data.frame")
 
-ns <- NetworkSummary(movements, root = 15, tEnd = '2010-08-31', days = 30)
+ns <- NetworkSummary(movements, root = 15, tEnd = "2010-08-31", days = 30)
 stopifnot(identical(ns$outDegree, 0L))
 
 ##
@@ -296,25 +296,25 @@ movements <- structure(list(source = c("2019", "2019", "2019", "2019", "2019",
 159L, 160L, 161L, 162L, 163L, 164L, 165L, 166L, 167L, 168L, 169L,
 170L, 171L, 172L), class = "data.frame")
 
-ct.1 <- Trace(movements, 2645, '2005-10-31', 90)
-ct.1.df <- as(ct.1, 'data.frame')
+ct.1 <- Trace(movements, 2645, "2005-10-31", 90)
+ct.1.df <- as(ct.1, "data.frame")
 
-ct.2 <- Trace(ct.1.df, 2645, '2005-10-31', 90)
-ct.2.df <- as(ct.2, 'data.frame')
+ct.2 <- Trace(ct.1.df, 2645, "2005-10-31", 90)
+ct.2.df <- as(ct.2, "data.frame")
 
-ct.1.df <- ct.1.df[, c('source',
-                       'destination',
-                       't',
-                       'id',
-                       'n',
-                       'category')]
+ct.1.df <- ct.1.df[, c("source",
+                       "destination",
+                       "t",
+                       "id",
+                       "n",
+                       "category")]
 
-ct.2.df <- ct.2.df[, c('source',
-                       'destination',
-                       't',
-                       'id',
-                       'n',
-                       'category')]
+ct.2.df <- ct.2.df[, c("source",
+                       "destination",
+                       "t",
+                       "id",
+                       "n",
+                       "category")]
 
 ct.1.df <- ct.1.df[order(ct.1.df$source,
                          ct.1.df$destination,
diff --git a/tests/network-summary.R b/tests/network-summary.R
index 868993a..9d9274e 100644
--- a/tests/network-summary.R
+++ b/tests/network-summary.R
@@ -30,15 +30,15 @@ data(transfers)
 ##
 load(file=system.file("extdata", "ns.rda", package="EpiContactTrace"))
 root <- sort(unique(c(transfers$source, transfers$destination)))
-result <- NetworkSummary(transfers, root=root, tEnd='2005-10-31', days=90)
+result <- NetworkSummary(transfers, root=root, tEnd="2005-10-31", days=90)
 stopifnot(identical(result, ns))
 
 ##
 ## Case 2
 ##
-ns <- NetworkSummary(transfers, root=584, tEnd='2005-10-31', days=91)
+ns <- NetworkSummary(transfers, root=584, tEnd="2005-10-31", days=91)
 ns.trace <- NetworkSummary(Trace(transfers,
                                  root=584,
-                                 tEnd='2005-10-31',
+                                 tEnd="2005-10-31",
                                  days=91))
 stopifnot(identical(ns, ns.trace))
diff --git a/tests/shortest-paths.R b/tests/shortest-paths.R
index 12eda30..9ff23b3 100644
--- a/tests/shortest-paths.R
+++ b/tests/shortest-paths.R
@@ -28,17 +28,17 @@ data(transfers)
 ##
 ## Case 1
 ##
-sp.1 <- ShortestPaths(transfers, root=2645, tEnd='2005-10-31', days=90)
-sp.2 <- ShortestPaths(Trace(movements=transfers, root=2645, tEnd='2005-10-31', days=90))
-in.1 <- sp.1[sp.1$direction == 'in', c('source', 'distance')]
-in.2 <- sp.2[sp.2$direction == 'in', c('source', 'distance')]
+sp.1 <- ShortestPaths(transfers, root=2645, tEnd="2005-10-31", days=90)
+sp.2 <- ShortestPaths(Trace(movements=transfers, root=2645, tEnd="2005-10-31", days=90))
+in.1 <- sp.1[sp.1$direction == "in", c("source", "distance")]
+in.2 <- sp.2[sp.2$direction == "in", c("source", "distance")]
 in.1 <- in.1[order(in.1$source, in.1$distance),]
 in.2 <- in.2[order(in.2$source, in.2$distance),]
 rownames(in.1) <- NULL
 rownames(in.2) <- NULL
 stopifnot(identical(in.1, in.2))
-out.1 <- sp.1[sp.1$direction == 'out', c('destination', 'distance')]
-out.2 <- sp.2[sp.2$direction == 'out', c('destination', 'distance')]
+out.1 <- sp.1[sp.1$direction == "out", c("destination", "distance")]
+out.2 <- sp.2[sp.2$direction == "out", c("destination", "distance")]
 out.1 <- out.1[order(out.1$destination, out.1$distance),]
 out.2 <- out.2[order(out.2$destination, out.2$distance),]
 rownames(out.1) <- NULL
@@ -54,8 +54,8 @@ sp.in.exp <- structure(list(root = c("100", "100", "100", "100", "100"),
                        .Names = c("root", "source", "distance"),
                        row.names = c(NA, -5L),
                        class = "data.frame")
-sp.in <- ShortestPaths(Trace(movements=transfers, root=100, tEnd='2005-10-31', days=90))
-sp.in <- sp.in[sp.in$direction == 'in', c('root', 'source', 'distance')]
+sp.in <- ShortestPaths(Trace(movements=transfers, root=100, tEnd="2005-10-31", days=90))
+sp.in <- sp.in[sp.in$direction == "in", c("root", "source", "distance")]
 sp.in <- sp.in[order(as.numeric(sp.in$source)),]
 rownames(sp.in) <- NULL
 stopifnot(identical(sp.in, sp.in.exp))
@@ -68,8 +68,8 @@ sp.out.exp <- structure(list(
     distance = c(1L, 1L, 1L, 2L, 1L, 2L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 3L)),
                         .Names = c("root", "destination", "distance"),
                         row.names = c(NA, -14L), class = "data.frame")
-sp.out <- ShortestPaths(Trace(movements=transfers, root=100, tEnd='2005-10-31', days=90))
-sp.out <- sp.out[sp.out$direction == 'out', c('root', 'destination', 'distance')]
+sp.out <- ShortestPaths(Trace(movements=transfers, root=100, tEnd="2005-10-31", days=90))
+sp.out <- sp.out[sp.out$direction == "out", c("root", "destination", "distance")]
 sp.out <- sp.out[order(as.numeric(sp.out$destination)),]
 rownames(sp.out) <- NULL
 stopifnot(identical(sp.out, sp.out.exp))