[mongodbreceiver] Fix get mongodb version (open-telemetry#27442)

**Description:** <Describe what has changed.>
- Improve the unit-test to catch similar errors in the future. 
- Fix mongodb version collection. 

**Link to tracking Issue:** <Issue number if applicable>
open-telemetry#27441 
**Testing:** <Describe what testing was performed and which tests were
added.>
Added the expectation assert for the Mock. 
This is the log output from running the tests in the first catching the
bug
```
--- FAIL: TestScraperScrape (0.00s)
    --- FAIL: TestScraperScrape/Failed_to_fetch_database_names (0.00s)
        pathTo/opentelemetry-collector-contrib/receiver/mongodbreceiver/scraper_test.go:316: FAIL:	GetVersion(string)
            		at: [pathTo/opentelemetry-collector-contrib/receiver/mongodbreceiver/scraper_test.go:146 pathTo/opentelemetry-collector-contrib/receiver/mongodbreceiver/scraper_test.go:292]
        pathTo/opentelemetry-collector-contrib/receiver/mongodbreceiver/scraper_test.go:316: PASS:	ListDatabaseNames(string,string,string)
        pathTo/opentelemetry-collector-contrib/receiver/mongodbreceiver/scraper_test.go:316: FAIL: 1 out of 2 expectation(s) were met.
            	The code you are testing needs to make 1 more call(s).
            	at: [pathTo/opentelemetry-collector-contrib/receiver/mongodbreceiver/scraper_test.go:316]
```
**Documentation:** <Describe the documentation added.>

.chloggen/receiver-mongodb-fix-get-version.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: 'bug_fix'
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: mongodbreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: "Fix mongo version not being collected"
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [27441]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

receiver/mongodbreceiver/scraper.go

@@ -21,6 +21,8 @@ import (
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/mongodbreceiver/internal/metadata"
 )
 
+var unknownVersion = func() *version.Version { return version.Must(version.NewVersion("0.0")) }
+
 type mongodbScraper struct {
 	logger       *zap.Logger
 	config       *Config
@@ -30,12 +32,11 @@ type mongodbScraper struct {
 }
 
 func newMongodbScraper(settings receiver.CreateSettings, config *Config) *mongodbScraper {
-	v, _ := version.NewVersion("0.0")
 	return &mongodbScraper{
 		logger:       settings.Logger,
 		config:       config,
 		mb:           metadata.NewMetricsBuilder(config.MetricsBuilderConfig, settings),
-		mongoVersion: v,
+		mongoVersion: unknownVersion(),
 	}
 }
 
@@ -60,7 +61,7 @@ func (s *mongodbScraper) scrape(ctx context.Context) (pmetric.Metrics, error) {
 		return pmetric.NewMetrics(), errors.New("no client was initialized before calling scrape")
 	}
 
-	if s.mongoVersion == nil {
+	if s.mongoVersion.Equal(unknownVersion()) {
 		version, err := s.client.GetVersion(ctx)
 		if err == nil {
 			s.mongoVersion = version

receiver/mongodbreceiver/scraper_test.go

@@ -121,14 +121,14 @@ func TestScraperScrape(t *testing.T) {
 	testCases := []struct {
 		desc              string
 		partialErr        bool
-		setupMockClient   func(t *testing.T) client
+		setupMockClient   func(t *testing.T) *fakeClient
 		expectedMetricGen func(t *testing.T) pmetric.Metrics
 		expectedErr       error
 	}{
 		{
 			desc:       "Nil client",
 			partialErr: false,
-			setupMockClient: func(t *testing.T) client {
+			setupMockClient: func(t *testing.T) *fakeClient {
 				return nil
 			},
 			expectedMetricGen: func(t *testing.T) pmetric.Metrics {
@@ -139,7 +139,7 @@ func TestScraperScrape(t *testing.T) {
 		{
 			desc:       "Failed to fetch database names",
 			partialErr: true,
-			setupMockClient: func(t *testing.T) client {
+			setupMockClient: func(t *testing.T) *fakeClient {
 				fc := &fakeClient{}
 				mongo40, err := version.NewVersion("4.0")
 				require.NoError(t, err)
@@ -155,7 +155,7 @@ func TestScraperScrape(t *testing.T) {
 		{
 			desc:       "Failed to fetch collection names",
 			partialErr: true,
-			setupMockClient: func(t *testing.T) client {
+			setupMockClient: func(t *testing.T) *fakeClient {
 				fc := &fakeClient{}
 				mongo40, err := version.NewVersion("4.0")
 				require.NoError(t, err)
@@ -181,7 +181,7 @@ func TestScraperScrape(t *testing.T) {
 		{
 			desc:       "Failed to scrape client stats",
 			partialErr: true,
-			setupMockClient: func(t *testing.T) client {
+			setupMockClient: func(t *testing.T) *fakeClient {
 				fc := &fakeClient{}
 				mongo40, err := version.NewVersion("4.0")
 				require.NoError(t, err)
@@ -209,7 +209,7 @@ func TestScraperScrape(t *testing.T) {
 		{
 			desc:       "Failed to scrape with partial errors on metrics",
 			partialErr: true,
-			setupMockClient: func(t *testing.T) client {
+			setupMockClient: func(t *testing.T) *fakeClient {
 				fc := &fakeClient{}
 				mongo40, err := version.NewVersion("4.0")
 				require.NoError(t, err)
@@ -240,7 +240,7 @@ func TestScraperScrape(t *testing.T) {
 		{
 			desc:       "Successful scrape",
 			partialErr: false,
-			setupMockClient: func(t *testing.T) client {
+			setupMockClient: func(t *testing.T) *fakeClient {
 				fc := &fakeClient{}
 				adminStatus, err := loadAdminStatusAsMap()
 				require.NoError(t, err)
@@ -288,7 +288,12 @@ func TestScraperScrape(t *testing.T) {
 			scraperCfg.MetricsBuilderConfig.Metrics.MongodbHealth.Enabled = true
 
 			scraper := newMongodbScraper(receivertest.NewNopCreateSettings(), scraperCfg)
-			scraper.client = tc.setupMockClient(t)
+
+			mc := tc.setupMockClient(t)
+			if mc != nil {
+				scraper.client = mc
+			}
+
 			actualMetrics, err := scraper.scrape(context.Background())
 			if tc.expectedErr == nil {
 				require.NoError(t, err)
@@ -307,6 +312,10 @@ func TestScraperScrape(t *testing.T) {
 				}
 			}
 
+			if mc != nil {
+				mc.AssertExpectations(t)
+			}
+
 			if tc.partialErr {
 				require.True(t, scrapererror.IsPartialScrapeError(err))
 			} else {