Add an additional test of covidcast_signal

Fetching multiple days is important.

Author: capnrefsmmat

R-packages/covidcast/tests/testthat/api.covidcast.cmu.edu/epidata/api.php-32641f.csv

@@ -0,0 +1,3 @@
+geo_value,signal,time_value,direction,issue,lag,value,stderr,sample_size
+01001,bar,20200110,,20200111,1,91.2,0.8,114.2
+01002,bar,20200110,,20200111,1,99.1,0.2,217.8

R-packages/covidcast/tests/testthat/api.covidcast.cmu.edu/epidata/api.php-b85d44.csv

@@ -0,0 +1,3 @@
+geo_value,signal,time_value,direction,issue,lag,value,stderr,sample_size
+31001,bar,20200112,,20200113,1,81.2,0.8,314.2
+31002,bar,20200112,,20200113,1,89.1,0.2,417.8

R-packages/covidcast/tests/testthat/api.covidcast.cmu.edu/epidata/api.php-f49e8f.csv

@@ -123,6 +123,49 @@ with_mock_api({
     )
   })
 
+  test_that("covidcast_signal works across multiple days with gaps", {
+    # If we request 3 days, we'll get 3 API queries. If the middle day is
+    # missing, we should get an appropriate warning, but still get the right
+    # data frame.
+
+    # day 1: api.php-32641f.csv
+    # day 2: api.php-b85d44.csv (empty)
+    # day 3: api.php-f49e8f.csv
+    expect_warning(covidcast_signal("foo", "bar", "2020-01-10", "2020-01-12",
+                                    geo_type = "county"),
+                   class = "covidcast_fetch_failed")
+
+    res <- suppressWarnings(
+      covidcast_signal("foo", "bar", "2020-01-10", "2020-01-12",
+                       geo_type = "county"))
+    expect_equal(
+      res,
+      structure(data.frame(
+        data_source = "foo",
+        signal = "bar",
+        geo_value = c("01001", "01002", "31001", "31002"),
+        time_value = as.Date(c("2020-01-10", "2020-01-10",
+                               "2020-01-12", "2020-01-12")),
+        issue = as.Date(c("2020-01-11", "2020-01-11",
+                          "2020-01-13", "2020-01-13")),
+        lag = 1,
+        value = c(91.2, 99.1, 81.2, 89.1),
+        stderr = c(0.8, 0.2, 0.8, 0.2),
+        sample_size = c(114.2, 217.8, 314.2, 417.8)),
+        class = c("covidcast_signal", "data.frame"),
+        metadata = structure(data.frame(
+          data_source = "foo",
+          signal = "bar",
+          time_type = "day",
+          geo_type = "county",
+          min_time = as.Date("2020-01-01"),
+          max_time = as.Date("2020-01-02"),
+          min_value = 0,
+          max_value = 10,
+          max_issue = as.Date("2020-04-04")),
+          class = c("covidcast_meta", "data.frame"))))
+  })
+
   test_that("covidcast_signal stops when end_day < start_day", {
     # reusing api.php-d2e163.json for metadata
     expect_error(covidcast_signal("foo", "bar", "2020-01-02", "2020-01-01"))